Method for manufacturing a semiconductor device

ABSTRACT

When a conductive layer is formed, a first liquid composition containing a conductive material is applied on an outer side of a pattern that is desired to be formed (corresponding to a contour or an edge portion of a pattern), and a first conductive layer (insulating layer) having a frame-shape is formed. A second liquid composition containing a conductive material is applied so as to fill a space inside the first conductive layer having a frame-shape, whereby a second conductive layer is formed. The first conductive layer and the second conductive layer are formed so as to be in contact with each other, and the first conductive layer is formed so as to surround the second conductive layer. Therefore, the first conductive layer and the second conductive layer can be used as one continuous conductive layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for manufacturing a displaydevice, using a printing method.

2. Description of the Related Art

In a thin film transistor (hereinafter also referred to as a TFT) and anelectronic circuit using the thin film transistor, various thin filmssuch as a semiconductor film, an insulating film, and a conductive filmare stacked over a substrate, and they are appropriately formed intopredetermined patterns by a photolithography technique. Thephotolithography technique is a technique in which a pattern of acircuit or the like which is formed using a material that does nottransmit light over a transparent flat plate, which is referred to as aphotomask, is transferred to an aimed substrate by using light. Thephotolithography technique is widely used in a manufacturing process ofa semiconductor integrated circuit and the like.

The conventional manufacturing process using the photolithographytechnique requires multiple steps such as exposure, development, baking,and peeling only for treating a mask pattern formed by using aphotosensitive organic resin material that is referred to as aphotoresist. Therefore, the manufacturing cost is inevitably increasedas the number of the photolithography steps is increased. In order tosolve this problem, it has been attempted to manufacture TFTs with thelower number of photolithography steps (refer to Patent Document 1:Japanese Published Patent Application No. 2000-133636). In PatentDocument 1, a resist mask formed in a photolithography step is usedonce, and then reused as a resist mask having a different shape byexpanding its volume by swelling.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a technique formanufacturing a TFT, an electronic circuit using the TFT, and a displaydevice formed using the TFT with a high yield at low cost, in which thenumber of photolithography steps is reduced and the manufacturingprocess is simplified, even in the case of a large substrate having aside of 1 meter or more.

Further, it is another object of the present invention to provide atechnique for forming a component such as a wiring included in thedisplay device into a desired shape with high controllability.

In the present invention, a conductive layer (insulating layer) isselectively formed so as to have a desired shape without using aphotolithography step. In particular, defects in shape or lack ofcontrollability of a conductive layer (insulating layer) can reduce ayield and reliability of a display device that is obtained.

In the present invention, a liquid composition is applied to a regionwhere a conductive layer (insulating layer) is formed and solidified bybaking, drying, and the like to form the conductive layer (insulatinglayer). In the case of such a method, the liquid composition needs to beapplied to the formation region in a minute and precise pattern toimprove precision of the shape or formation region of the conductivelayer (insulating layer). In particular, when a wiring layer for forminga circuit is formed, displacement of a region where the wiring layer isformed adversely affects electric characteristics, and for example, ashort circuit may be caused.

Therefore, in a method for forming a conductive layer (insulating layer)shown in the present invention, a conductive layer (insulating layer) isformed through at least two steps. When the conductive layer (insulatinglayer) is formed, a first liquid composition containing a conductive(insulating) material is applied on an outer side of a pattern that isdesired to be formed (corresponding to a contour or an edge portion of apattern), and a first conductive layer (insulating layer) having aframe-shape is formed. The first conductive layer (insulating layer) ispreferably a closed region like a frame. Next, a second liquidcomposition containing a conductive (insulating) material is applied soas to fill a space inside the first conductive layer (insulating layer)having a frame-shape, and a second conductive (insulating) layer isformed. The first conductive layer (insulating layer) and the secondconductive layer (insulating layer) are formed so as to be in contactwith each other, and the first conductive layer (insulating layer) isformed so as to surround the second conductive layer (insulating layer).Therefore, the first conductive layer (insulating layer) and the secondconductive layer (insulating layer) can be used as one continuousconductive layer (insulating layer).

When a conductive layer (insulating layer) or the like is formed using aliquid composition, a shape of a conductive layer (insulating layer)that is formed is greatly influenced by the viscosity of a composition,drying conditions in solidification (such as temperature or pressure),wettability with respect to a formation region, and the like. Therefore,with low viscosity or high wattability with respect to a formationregion, a liquid composition spreads over a formation region. On theother hand, with high viscosity or low wettability with respect to aformation region, space (also referred to as pin holes) and unevennessare formed in or on the surface of the conductive layer (insulatinglayer), and a level of planarity is decreased.

Therefore, in the present invention, when the first conductive layer(insulating layer) which determines the contour of the formation regionof the conductive layer (insulating layer) is formed by applying acomposition with relatively high viscosity and low wettability withrespect to a formation region, a side edge portion which becomes acontour of a desired pattern can be formed with high controllability.When a composition with low viscosity and high wettability with respectto a formation region is applied inside a frame formed of the firstconductive layer (insulating layer), space, unevenness, and the like dueto bubbles and the like in or on the surface of the conductive layer arereduced, and a conductive layer (insulating layer) which is very flatand uniform can be formed. Therefore, by separate formation of anouter-side conductive layer (insulating layer) and an inner-sideconductive layer (insulating layer), a conductive layer (insulatinglayer) that has a high level of planarity, less defects, and a desiredpattern can be formed with high controllability.

When conductive layers are electrically connected with an insulatinglayer interposed therebetween, an opening (so called contact hole) isformed in the insulating layer. In this case, a mask layer is not formedover the insulating layer, and the opening is selectively formed bylaser beam irradiation. A first conductive layer is formed, aninsulating layer is stacked over the first conductive layer, and aregion where the opening is formed in the stacked first conductive layerand insulating layer is selectively irradiated with a laser beam fromthe insulating layer side. The laser beam is transmitted through theinsulating layer and absorbed by the first conductive layer. The firstconductive layer is heated by energy of the absorbed laser beam andevaporated, and the insulating layer that is stacked thereover isbroken. Therefore, the opening is formed in the first conductive layerand the insulating layer, and part of the conductive layer below theinsulating layer is exposed on the side wall and the bottom (or only onthe side wall) of the opening. By formation of a second conductive layerin the opening so as to be in contact with the exposed first conductivelayer, the first and second conductive layers can be electricallyconnected to each other with the insulating layer interposedtherebetween. In other words, in the present invention, the conductivelayer is irradiated with a laser beam, an irradiated region of theconductive layer with a laser beam is evaporated by laser ablation, andthe opening is formed in the insulating layer that is formed over theconductive layer.

Since the opening can be selectively formed by a laser beam, a masklayer does not need to be formed, and the steps and materials can bereduced. In addition, there are advantages that a conductive layer andan insulating layer to be processed can be formed into a predeterminedshape with high precision since the laser beam can be condensed into avery small spot, and the regions other than the processing region do notneed to be heated substantially since heating is performed in a shorttime by the laser beam.

The present invention can also be applied to a display device that is adevice having a display function, and the display device using thepresent invention includes a light-emitting display device in which alight-emitting element including a layer containing an organic material,an inorganic material, or a mixture of an organic material and aninorganic material, which exhibits light-emission calledelectroluminescence (hereinafter also refereed to as EL) and interposedbetween electrodes is connected to a TFT; a liquid crystal displaydevice using a liquid crystal element containing a liquid crystalmaterial as a display element; and the like.

One aspect of the present invention is a method for manufacturing adisplay device, including the steps of forming a first conductive layerhaving a frame-shape over a substrate having an insulating surface bydischarging a first composition containing a conductive material; andforming a second conductive layer inside a frame formed of the firstconductive layer by discharging a second composition containing aconductive material in a region surrounded by the first conductive layerhaving the frame-shape.

Another aspect of the present invention is a method for manufacturing adisplay device, including the steps of forming a first conductive layerhaving a frame-shape over a substrate having an insulating surface bydischarging a first composition containing a conductive material; andforming a second conductive layer inside a frame formed of the firstconductive layer by discharging a second composition containing aconductive material in a region surrounded by the first conductive layerhaving the frame-shape. The viscosity of the first compositioncontaining a conductive material is higher than the viscosity of thesecond composition containing a conductive material.

Another aspect of the present invention is a method for manufacturing adisplay device, including the steps of forming a first conductive layerhaving a frame-shape over a substrate having an insulating surface bydischarging a first composition containing a conductive material; andforming a second conductive layer inside a frame formed of the firstconductive layer by discharging a second composition containing aconductive material in a region surrounded by the first conductive layerhaving the frame-shape. Wettability of the first composition containinga conductive material with respect to the substrate having an insulatingsurface is lower than wettability of the second composition containing aconductive material with respect to the substrate having an insulatingsurface.

In the above aspects, the first composition containing a conductivematerial and the second composition containing a conductive material maybe continuously discharged or intermittently discharged in a dropletstate. For example, when the first conductive layer positioned on theouter side of the conductive layer in a frame-shape is formed, the firstcomposition containing a conductive material may be continuouslydischarged, whereas, when the second conductive layer is formed so as tofill inside the frame formed of the first conductive layer, the secondcomposition containing a conductive material may be intermittentlydischarged. In such a manner, a method for discharging a liquidcomposition may be varied depending on a pattern to be formed.

In addition, the first conductive layer and the second conductive layerformed in different steps may have almost the same thickness ordifferent thicknesses. For example, the first conductive layer formed inthe first step has a frame-shape, and the second composition containinga conductive material is discharged to have a height (thickness) lowerthan that of the frame of the first conductive layer, and the secondconductive layer is formed, whereby the thickness of the firstconductive layer can be larger than that of the second conductive layer.

The conductive layer formed as described above can be used as anyconductive layer included in the display device. For example, theconductive layer can be used for a wiring layer, a gate electrode layer,a source electrode layer, a drain electrode layer, a pixel electrodelayer, and the like. In addition, a method for manufacturing aconductive layer, for example, for manufacturing the first conductivelayer having a frame-shape and the second conductive layer inside theframe formed of the first conductive layer, can also be used for aninsulating layer. For example, the method can also be used for aninsulating layer functioning as a partition wall and the like.

Another aspect of the present invention is a method for manufacturing adisplay device, including the steps of forming a first conductive layer;forming an insulating layer over the first conductive layer; forming anopening in the first conductive layer and the insulating layer byselectively irradiating the first conductive layer and the insulatinglayer with a laser beam to remove part of an irradiated region of thefirst conductive layer and an irradiated region of the insulating layer;and forming a second conductive layer electrically connected to thefirst conductive layer by discharging a composition containing aconductive material in the opening.

Another aspect of the present invention is a method for manufacturing adisplay device, including the steps of forming a first conductive layer;forming a second conductive layer over the first conductive layer;forming an insulating layer over the first conductive layer and thesecond conductive layer; forming an opening in the second conductivelayer and the insulating layer by selectively irradiating the firstconductive layer, the second conductive layer, and the insulating layerwith a laser beam to remove an irradiated region of the secondconductive layer and an irradiated region of the insulating layer; andforming a third conductive layer electrically connected to the firstconductive layer and the second conductive layer by discharging acomposition containing a conductive material in the opening.

In the above aspects, the conductive layer in which the opening isformed can be formed using at least one of chromium, molybdenum, nickel,titanium, cobalt, copper, and aluminum. Further, the insulating layer inwhich the opening is formed can be formed using a material whichtransmits the laser beam therethrough, such as a light-transmittingorganic resin.

In accordance with the present invention, a component such as a wiringincluded in a display device or the like can be formed into a desiredshape. In addition, since complicated photolithography steps can bereduced and a display device can be manufactured through a simplifiedprocess, loss of materials and the cost can be reduced. Therefore, ahigh performance and highly reliable display device can be manufacturedwith a high yield.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A-1 to 1B-2 are explanatory schematic views of the presentinvention;

FIGS. 2A to 2C are explanatory schematic views of the present invention;

FIGS. 3A to 3C are explanatory schematic views of the present invention;

FIGS. 4A to 4D are explanatory schematic views of the present invention;

FIGS. 5A to 5D are explanatory schematic views of the present invention;

FIGS. 6A to 6C are explanatory schematic views of the present invention;

FIGS. 7A to 7C are explanatory views of a method for manufacturing adisplay device of the present invention;

FIGS. 8A to 8C are explanatory views of a method for manufacturing adisplay device of the present invention;

FIGS. 9A to 9C are explanatory views of a method for manufacturing adisplay device of the present invention;

FIGS. 10A to 10C are explanatory views of a method for manufacturing adisplay device of the present invention;

FIGS. 11A to 11C are explanatory views of a method for manufacturing adisplay device of the present invention;

FIGS. 12A to 12C are explanatory views of a method for manufacturing adisplay device of the present invention;

FIGS. 13A to 13C are explanatory views of a method for manufacturing adisplay device of the present invention;

FIGS. 14A and 14B are explanatory views of a method for manufacturing adisplay device of the present invention;

FIGS. 15A and 15B are explanatory views of a display device of thepresent invention;

FIG. 16 is an explanatory cross-sectional view of a structural exampleof a display module of the present invention;

FIGS. 17A to 17C are explanatory views of a display device of thepresent invention;

FIG. 18 is an explanatory view of a display device of the presentinvention;

FIGS. 19A and 19B are explanatory views of a method for manufacturing adisplay device of the present invention;

FIGS. 20A and 20B are explanatory cross-sectional views of a structuralexample of a display module of the present invention;

FIG. 21 is an explanatory view of a display device of the presentinvention;

FIGS. 22A to 22D are explanatory views of a structure of alight-emitting element which can be applied to the present invention;

FIGS. 23A to 23C are explanatory views of a structure of alight-emitting element which can be applied to the present invention;

FIGS. 24A to 24C are explanatory views of a structure of alight-emitting element which can be applied to the present invention;

FIGS. 25 A to 25C are top views of a display device of the presentinvention;

FIGS. 26A and 26B are top views of a display device of the presentinvention;

FIG. 27 is a block diagram showing a main structure of an electronicdevice to which the present invention is applied;

FIGS. 28A and 28B are views showing electronic devices to which thepresent invention is applied;

FIGS. 29A to 29E are views showing electronic devices to which thepresent invention is applied;

FIG. 30 is an explanatory view of a structure of a droplet dischargingapparatus which can be applied to the present invention;

FIG. 31 is an explanatory diagram of a structure of a laser beam directwriting system which can be applied to the present invention;

FIG. 32 is an explanatory diagram of a circuit configuration in a casewhere a scanning line driver circuit is formed using a TFT in a displaypanel of the present invention;

FIG. 33 is an explanatory diagram of a circuit configuration (shiftregister circuit) in a case where a scanning line driver circuit isformed using a TFT in a display panel of the present invention;

FIG. 34 is an explanatory diagram of a circuit configuration (buffercircuit) in a case where a scanning line driver circuit is formed usinga TFT in a display panel of the present invention;

FIGS. 35A to 35D are explanatory schematic views of the presentinvention;

FIG. 36 is an explanatory view of a method for manufacturing a displaydevice of the present invention;

FIG. 37 is an explanatory view of a method for manufacturing a displaydevice of the present invention; and

FIG. 38 is an explanatory view of a method for manufacturing a displaydevice of the present invention.

DESCRIPTION OF THE INVENTION

Embodiment Modes of the present invention will be described in detailwith reference to the accompanying drawings. It is to be noted that thepresent invention is not limited to the following description, and it iseasily understood by those skilled in the art that modes and detailsthereof can be modified in various ways without departing from thespirit and the scope of the present invention. Therefore, the presentinvention should not be interpreted as being limited to the followingdescription of the embodiment modes. In a structure of the presentinvention to be given below, the same portions or portions havingsimilar functions are denoted by the same reference numerals indifferent drawings, and explanation thereof will be omitted.

Embodiment Mode 1

In this embodiment mode, a method for manufacturing a highly reliabledisplay device through a simplified process at low cost will bedescribed with reference to FIGS. 1A-1 to 1B-2, and 2A to 2C.

In accordance with the present invention, a display device ismanufactured in such a way that at least one of components necessary forforming a display device or the like, such as a conductive layer forforming a wiring layer or an electrode is formed by a method by whichthe components can be selectively formed into a desired shape. In thepresent invention, the components (also called patterns) are aconductive layer such as a wiring layer, a gate electrode layer, asource electrode layer, or a drain electrode layer, a semiconductorlayer, a mask layer, an insulating layer, and the like included in athin film transistor or a display device and include all the componentsformed to have a predetermined shape. As the method by which an objectcan be selectively formed into a desired pattern, a droplet discharging(jetting) method (also called an ink jet method depending on its system)by which a conductive layer, an insulating layer, or the like can beformed into a predetermined pattern by selectively discharging (jetting)a droplet of a composition which is mixed for a particular purpose isused. In addition, a method by which a component can be formed into adesired pattern by transferring or drawing, for example, variousprinting methods (a method for forming a component into a desiredpattern, such as screen (mimeograph) printing, offset (planograph)printing, relief printing, or gravure (intaglio) printing), a dispensermethod, a selective-coating method, or the like can also be used.

In this embodiment mode, a method for forming a component into a desiredpattern by discharging Getting) a composition containing acomponent-forming material which is a fluid as a droplet is used. In aregion where the component is formed, the droplet containing thecomponent-forming material is discharged, and baked, dried, and the liketo be solidified, whereby the component is formed into a desiredpattern.

One mode of a droplet discharging apparatus used for a dropletdischarging method is shown in FIG. 30. Each of heads 1405 and 1412 of adroplet discharging unit 1403 is connected to a control device 1407, andthis control device 1407 is controlled by a computer 1410, whereby apreprogrammed pattern can be drawn. The formation position may bedetermined, for example, based on a marker 1411 that is formed over asubstrate 1400. Alternatively, a reference point may be fixed based onthe edge of the substrate 1400. The reference point is detected by animaging device 1404, and changed into a digital signal using an imageprocessing unit 1409. Then, the digital signal is recognized by thecomputer 1410, the computer 1410 generates a control signal, and thecontrol signal is transmitted to the control device 1407. An imagesensor or the like using a charge coupled device (CCD) or acomplementary metal oxide semiconductor can be used for the imagingdevice 1404. Data about a pattern to be formed over the substrate 1400is stored in a storage medium 1408, and the control signal istransmitted to the control device 1407 based on the data, so that eachof the heads 1405 and 1412 of the droplet discharging unit 1403 can beindividually controlled. A material to be discharged is supplied to theheads 1405 and 1412 from material supply sources 1413 and 1414 throughpipes, respectively.

The head 1405 has an inside structure which has a space to be filledwith a liquid material as shown by dotted lines 1406 and a nozzle whichis a discharging outlet. Although it is not shown, the inside structureof the head 1412 is similar to that of the head 1405. When the nozzlesizes of the heads 1405 and 1412 are different from each other,different materials can be discharged concurrently to have differentwidths. A conductive material, an organic material, an inorganicmaterial, and the like can be each discharged from one head to be drawn.In a case of drawing over a large area such as an interlayer film, onematerial can be concurrently discharged from a plurality of nozzles fordrawing to improve throughput. When a large substrate is used, the heads1405 and 1412 can freely scan over the substrate in directions indicatedby arrows, and a region in which drawing is performed can be freely set.Thus, a plurality of the same patterns can be drawn over one substrate.

In the case where a conductive layer is formed by a droplet dischargingmethod, a composition containing particles of a conductive material isdischarged, and fused or welded by baking to be solidified, so that aconductive layer is formed. A conductive layer (or an insulating layer)formed by discharging and baking a composition containing a conductivematerial has, in many cases, a polycrystalline state with many grainboundaries whereas a conductive layer (or an insulating layer) formed bya sputtering method or the like has, in many cases, a columnarstructure.

The general idea of the embodiment mode of the present invention will bedescribed using a method for forming a conductive layer with referenceto FIGS. 1A-1 to 1B-2, and 2A to 2C. FIGS. 1A-2 and 1B-2 are top viewsof a conductive layer, and FIGS. 1A-1 and 1B-1 are cross-sectional viewstaken along lines Y-Z in FIGS. 1A-2 and 1B-2.

In the present invention, a conductive layer is selectively formed tohave a desired shape without using a photolithography step. A defectiveshape and lack of controllability such as deformation of a conductivelayer and displacement in formation can cause reduction in yield andreliability of a display device which is obtained.

In the present invention, a liquid composition is applied to a regionwhere a conductive layer (insulating layer) is formed and solidified bybaking, drying, and the like to form the conductive layer (insulatinglayer). In such a method, the liquid composition needs to be applied tothe formation region in a minute and precise pattern to improveprecision of the shape and formation region of the conductive layer(insulating layer). In particular, when a wiring layer for forming acircuit is formed, displacement of a region where the wiring layer isformed adversely affects electric characteristics, and for example, ashort circuit may be caused.

Therefore, in a method for forming a conductive layer (insulating layer)shown in the present invention, a conductive layer (insulating layer) isformed through at least two steps. When the conductive layer (insulatinglayer) is formed, a first liquid composition containing a conductive(insulating) material is applied on an outer side of a pattern that isdesired to be formed (corresponding to a contour or an edge portion of apattern), and a first conductive layer (insulating layer) having aframe-shape is formed. The first conductive layer (insulating layer) ispreferably a closed region like a frame. In this embodiment mode, aliquid composition containing a conductive material is discharged withthe use of droplet discharging apparatuses 702 a and 702 b to asubstrate 700, whereby a first conductive layer 703 (703 a and 703 b) isformed. The first conductive layer 703 is formed so as to have a closedframe-shape along a contour or an edge portion of a pattern of aconductive layer to be formed (refer to FIGS. 1A1 and 1A2).

Next, a second liquid composition containing a conductive (insulating)material is applied so as to fill the space inside the first conductivelayer (insulating layer) having a frame-shape, whereby a secondconductive layer (insulating layer) is formed. In this embodiment mode,the second liquid composition containing a conductive (insulating)material is discharged with the use of a droplet discharging apparatus704 so as to fill the space inside the first ring-shaped conductivelayer 703, whereby a second conductive layer 705 is formed (refer toFIGS. 1B1 and 1B2). The first conductive layer 703 and the secondconductive layer 705 are formed so as to be in contact with each other,and the first conductive layer 703 is formed so as to surround thesecond conductive layer 705. Therefore, the first conductive layer 703and the second conductive layer 705 can be used as one continuousconductive layer.

When a conductive layer or the like is formed using a liquidcomposition, a shape of a conductive layer to be formed is greatlyinfluenced by the viscosity of a composition, drying conditions insolidification (such as temperature or pressure), wettability withrespect to a formation region, and the like. Therefore, with lowviscosity or high wettability with respect to a formation region, aliquid composition spreads over a formation region. On the other hand,with high viscosity or low wettability with respect to a formationregion, there is a problem in that space (also referred to as pin holes)and unevenness are formed in or on the surface of the conductive layer,and a level of planarity is decreased.

Therefore, in the present invention, when the first conductive layer 703which determines a contour of a formation region of the conductive layeris formed by applying a composition with relatively high viscosity andlow wettability with respect to the formation region, a side edgeportion which becomes a contour of a desired pattern can be formed withhigh controllability. When a liquid composition with low viscosity andhigh wettability with respect to the formation region is applied insidea frame formed of the first conductive layer 703, space, unevenness, andthe like due to bubbles and the like formed in or on the surface of theconductive layer are reduced, and the second conductive layer 705 whichis very flat and uniform can be formed. Therefore, by separate formationof an outer-side conductive layer (the first conductive layer 703) andan inner-side conductive layer (the second conductive layer 705), aconductive layer that has a high level of planarity, less defects, and adesired pattern can be formed with high controllability.

The first composition containing a conductive material and the secondcomposition containing a conductive material may be dischargedcontinuously or may be discharged intermittently in a droplet state. Forexample, when the first conductive layer which is positioned on theouter side of the conductive layer in a frame shape is formed, the firstcomposition containing a conductive material may be dischargedcontinuously. On the other hand, when the second conductive layer whichis formed to fill the space inside the first conductive layer having aframe-shape is formed, the second composition containing a conductivematerial may be discharged intermittently. In such a manner, a method,for discharging a liquid composition may be varied depending on apattern to be formed. FIGS. 6A to 6C each show an example of a methodfor discharging a liquid composition.

In FIG. 6A, a composition containing a conductive material is dischargedfrom a droplet discharging apparatus 763 to a substrate 760, whereby aconductive layer 764 is formed. In FIG. 6A, the composition containing aconductive material is discharged intermittently.

In FIG. 6B, a composition containing a conductive material is dischargedfrom a droplet discharging apparatus 767 to a substrate 765, whereby aconductive layer 768 is formed. In FIG. 6B, the composition containing aconductive material is discharged continuously.

FIG. 6C is an example in which, over a substrate 770, a region where acomposition containing a conductive material is dischargedintermittently and a region where a composition containing a conductivematerial is discharged continuously are separately formed depending on ashape of a conductive layer to be formed. In FIG. 6C, a compositioncontaining a conductive material is discharged continuously from adroplet discharging apparatus 774, whereby a conductive layer 775 isformed, and a composition containing a conductive material is dischargedintermittently from a droplet discharging apparatus 772, whereby aconductive layer 773 is formed. In such a manner, a method fordischarging a liquid composition can be appropriately set depending on ashape of a conductive layer to be formed.

This embodiment mode shows the example in which a conductive layer isformed through two steps: forming a first conductive layer which forms aperipheral edge portion along a contour of a pattern and forming asecond conductive layer which fills the space inside the frame formed ofthe first conductive layer. Further, the first conductive layer in anouter frame may be formed through a plurality of steps, or the secondconductive layer which fills the space inside the frame formed of thefirst conductive layer may be formed through a plurality of steps.

Further, when a conductive layer is formed, a composition containing aninsulating material may be discharged along a contour of a region wherethe conductive layer is formed, so that an insulating layer having aframe-shape may be formed. A composition containing a conductivematerial may be discharged to fill the space inside the insulating layerhaving a frame-shape, so that the conductive layer surrounded by theinsulating layer can be formed. In such a manner, different materialscan be used for an object having a frame-shape which is an outer frameto determine a pattern and an object which is formed by being dischargedto fill the space inside the object having a frame-shape.

FIGS. 2A to 2C show examples of the first conductive layer and thesecond conductive layer having other shapes. FIGS. 2A to 2C correspondto FIG. 1B-1. FIG 1B-1 is an example in which the second conductivelayer is formed so that the second composition containing a conductivematerial is filled inside the frame formed of the first conductive layerso as not to extend beyond the frame, and the thickness of the secondconductive layer is smaller than that of the first conductive layer. InFIG. 2A, a second conductive layer 715 a is filled to have the heightwhich is roughly the same as that of first conductive layers 703 a and703 b, and the thickness of the second conductive layer 715 a is roughlythe same as that of the first conductive layers 703 a and 703 b. In thepresent invention, since the conductive layer is formed by applying aliquid composition to a formation region and thereafter solidifying thecomposition, as shown in FIGS. 2A to 2C, a conductive layer that isobtained is influenced by a shape of a liquid (droplet) and can beformed into a round shape having a curvature in the edge portions (aso-called dome-shape like the first conductive layer 703 a in FIGS. 2Ato 2C).

In FIG. 2B, a thickness of a second conductive layer 715 b gets largertoward the center. Although the thickness of the side edge portions ofthe second conductive layer 715 b that are in contact with firstconductive layers 703 a and 703 b is smaller than that of the firstconductive layers 703 a and 703 b, the thickness of the secondconductive layer 715 b in the center is larger than that of the firstconductive layers 703 a and 703 b. In FIG. 2C, a thickness of a secondconductive layer 715 c gets smaller toward the center. The thickness ofthe side edge portions of the second conductive layer 715 c that are incontact with first conductive layers 703 a and 703 b is smaller thanthat of the first conductive layers 703 a and 703 b, and the thicknessof the second conductive layer 715 c in the center is still smaller thanthat of the first conductive layers 703 a and 703 b. In such a manner,the shape of the second conductive layer can vary depending onwettability or the viscosity of the first and second conductive layers.Further, the shape of the conductive layer may be changed due to acondition of a liquid composition that has been just discharged orsolidification by drying (or heating). Such deformation of an objectafter solidification is caused due to a material, a solvent,solidification conditions (pressure, temperature, and time), and thelike; therefore, conditions may be appropriately set to obtain a desiredshape.

Wettability of a formation region may be controlled so that the firstconductive layer and the second conductive layer are selectively formed.FIGS. 3A to 3C show an example in which modification treatment isperformed to a region where a conductive layer is formed and a regionwhere a conductive layer is not formed so that the regions have adifference in wettability and a first conductive layer is formed withhigh controllability.

As shown in FIG. 3A, wettability of a surface of a substrate 700 iscontrolled so as to be varied selectively. In this embodiment mode, alow-wettability substance 701 is selectively formed over the substrate700, so that low-wettability regions 707 a, 707 b, and 707 c which havelower wettability (higher repellent property) than the peripheralportions are formed. Since the low-wettability regions 707 a, 707 b, and707 c which have low wettability (high repellent property) are formed,the peripheral regions become high-wettability regions 708 a and 708 bwhich have high wettability (high lyophilic property).

A first liquid composition containing a conductive material isdischarged from droplet discharging apparatuses 709 a and 709 b, andfirst conductive layers 710 a and 710 b are selectively formed in thehigh-wettability regions 708 a and 708 b. In such a manner, when aregion other than a region where the first conductive layer is formed isto be a repellent region with respect to the first compositioncontaining a conductive material, the first liquid compositioncontaining a conductive material does not spread over the formationregion and is applied to only the high-wettability regions 708 a and 708b with high controllability, whereby the first conductive layer can beformed.

Thereafter, the low-wettability substance is removed by ashing,ultraviolet (UV) light irradiation, and the like, a second compositioncontaining a conductive material is discharged from a dropletdischarging apparatus 711 to fill inside the frame formed of the firstconductive layers 710 a and 710 b, and a second conductive layer 712 isformed.

The liquid composition containing a conductive material is in a liquidstate, and thus, is greatly influenced by the surface state of theformation region. In the present invention, treatment for controllingwettability of a region where the liquid composition is applied may beperformed.

Wettability of a solid surface is influenced by chemical properties ofthe surface and the physical surface shape (roughness of the surface).If a substance having low wettability with respect to a liquidcomposition is formed, the solid surface is a region having lowwettability with respect to the liquid composition (hereinafter alsoreferred to as a low-wettability region). On the other hand, if asubstance having high wettability with respect to a liquid compositionis formed, the solid surface is a region having high wettability withrespect to the liquid composition (hereinafter also referred to as ahigh-wettability region). In the treatment for controlling surfacewettability of the present invention, regions with different wettabilitywith respect to a liquid composition are formed in a region where theliquid composition is applied.

The regions having different wettability have a difference inwettability with respect to a liquid composition, where contact anglesof a composition containing a conductive material are different fromeach other. A region where a contact angle of the composition containinga conductive material is large is a region having low wettability(hereinafter also referred to as a low-wettability region) and a regionwhere a contact angle is small is a region having high wettability(hereinafter also referred to as a high-wettability region). With alarge contact angle, a liquid composition having fluidity does notspread over a region surface, and the surface repels the composition andis not wetted thereby. With a small contact angle, a composition havingfluidity spreads over a surface., and the surface is wetted wellthereby. Therefore, the regions having different wettability havedifferent surface energy. The region having low wettability has lowsurface energy, and the region having high wettability has high surfaceenergy.

The difference in wettability is relative in the both regions. Two kindsof regions with different wettability can be formed by selectiveformation of a low-wettability region. As a method for selectivelyforming the low-wettability region, a method in which a low-wettabilitysubstance is selectively formed by forming and using a mask layer, amethod in which surface treatment is performed to lower wettabilityselectively with the use of a mask layer, or the like can be used.Alternatively, a method in which a low-wettability effect is selectivelyeliminated (removal or decomposition of a low-wettability substance)after formation of a low-wettability region, or the like can be used.

As a method for changing and controlling surface wettability, there is amethod in which wettability is changed by decomposing a surfacesubstance and modifying a region surface with the use of lightirradiation energy. As the low-wettability substance, a substancecontaining a fluorocarbon group (or fluorocarbon chain) or a substancecontaining a silane coupling agent can be used. The silane couplingagent can form a monomolecular film; therefore, decomposition andmodification can be efficiently carried out and wettability is changedin a short time. The monomolecular film can also be referred to as aself-assembled film. In addition, not only a silane coupling agenthaving a fluorocarbon group (or fluorocarbon chain) but also that havingan alkyl group can be used, because the silane coupling agent having analkyl group exhibits low wettability when arranged over a substrate.Further, as the low-wettability substance, a titanate coupling agent andan aluminate coupling agent may also be used.

In accordance with the present invention, regions with much differentwettability (regions having a large difference in wettability) can beformed. Thus, a liquid conductive (insulating) material is applied onlyto a formation region with high precision. Accordingly, a conductive(insulating) layer can be precisely formed into a desired pattern.

As the low-wettability substance, a substance containing a fluorocarbongroup (fluorocarbon chain) or a substance containing a silane couplingagent can be used. The silane coupling agent is expressed by thechemical formula: Rn—Si—X_(4-n) (n=1, 2, 3). In this chemical formula, Rrepresents a material containing a relatively inactive group such as analkyl group. X represents a hydrolytic group such as halogen, a methoxygroup, an ethoxy group, or an acetoxy group that is bondable by acondensation of a hydroxyl group or adsorbed water on a base materialsurface.

When a fluorine-based silane coupling agent which has a fluoroalkylgroup for R (such as fluoroalkylsilane (FAS)) is used as a typicalexample of the silane coupling agent, the wettability can be furtherlowered. R in FAS has a structure expressed by (CF₃)(CF₂)_(x)(CH₂)_(y)(x is an integer that is greater than or equal to 0 and less than orequal to 10, and y is an integer that is greater than or equal to 0 andless than or equal to 4). When a plurality of Rs or Xs are bonded to Si,the Rs or Xs may be all the same or different from one another.Typically, the following can be given as typical FAS: heptadecafluorotetrahydrodecyl triethoxysilane, heptadecafluoro tetrahydrodecyltrichlorosilane, tridecafluoro tetrahydrooctyl trichlorosilane,trifluoropropyl trimethoxysilane, or tridecafluoro octyltrimethoxysilane. Further, a coupling agent in which a hydrolytic groupof tridecafluoro octyl trichlorosilane or the like is halogen can alsobe used. Of course, the present invention is not limited to the abovecompounds.

Further, as the low-wettability substance, a titanate coupling agent oran aluminate coupling agent may be used. For example,isopropyltriisooctanoyl titanate,isopropyl(dioctylpyrophosphate)titanate, isopropyltristearoyl titanate,isopropyl tris(dioctylphosphate)titanate,isopropyldimethacrylisostearoyl titanate, acetoalkoxyaluminumdiisopropylate, or the like can be used.

When the above low-wettability substance is formed as a film in aformation region, a vapor deposition method for evaporating and forminga liquid substance in the formation region (such as a substrate) or thelike can be used. Further, the low-wettability substance may be formedby a spin coating method, a dipping method, a droplet dischargingmethod, and a printing method (such as screen printing or offsetprinting) and may also be dissolved in a solvent to be a solution.

For a solvent of a solution containing the low-wettability substance,water, alcohol, ketone, a hydrocarbon-based solvent (such as aliphatichydrocarbon, aromatic hydrocarbon, and halogenated hydrocarbon), anether-based compound, and a mixture thereof can be used. For example,methanol, ethanol, propanol, acetone, butanone, n-pentane, n-hexane,n-heptane, n-octane, n-decane, dicyclopentane, benzene, toluene, xylene,durene, indene, tetrahydronaphthalene, decahydronaphthalene, squalane,carbon tetrachloride, chloroform, methylene chloride, trichloroethane,diethyl ether, dioxane, dimethoxyethane, tetrahydrofran, or the like isused. The concentration of the above solution is not particularlylimited, and the concentration may be in a range of 0.001 to 20 wt %.

Further, amine such as pyridine, triethylamine, or dimethylaniline maybe mixed in the above low-wettability substance. Furthermore, carboxylicacid such as formic acid or acetic acid may be added as a catalystagent.

Treatment for forming a monomolecular film by a spin coating method orthe like in which a low-wettablity substance is applied to a formationregion in a liquid state as described above may be carried out at roomtemperature (about 25° C.) to 150° C. for several minutes to 12 hours.Treatment conditions may be appropriately set depending on acharacteristic of the low-wettability substance, the concentration of asolution, treatment temperature, and treatment time.

Further, as an example of a solution composition for forming alow-wettability region, a material having a fluorocarbon chain (afluorine-based resin) can be used. As the fluorine-based resin,polytetrafluoroethylene (PTFE; a tetrafluoroethylene resin),perfluoroalkoxyalkane (PFA; a tetrafluoroethyleneperfluoroalkylvinylether copolymer resin), perfluoroethylene propenecopolymer (PFEP; a tetrafluoroethylene-hexafluoropropylene copolymerresin), ethylene-tetrafluoroethylene copolymer (ETFE; atetrafluoroethylene-ethylene copolymer resin), polyvinylidene fluoride(PVDF; a polyvinylidene fluoride resin), polychlorotrifluoroethylene(PCTTE; a polytrifluorochloroethylene resin),ethylene-chlorotrifluoroethylene copolymer (ECTFE; apolytrifluorochloroethylene-ethylene copolymer resin),polytetrafluoroethylene-perfluorodioxol copolymer (TFE/PDD),polyvinylfluoride (PVF; a vinyl fluoride resin), or the like can beused.

Further, with the use of an organic material not having low wettability(that is, having high wettability), treatment by CF₄ plasma or the likemay be performed to form a low-wettability region. For example, amaterial in which a water-soluble resin such as polyvinyl alcohol (PVA)is mixed in a solvent such as H₂O can be used. In addition, acombination of PVA and another water-soluble resin can be used. Anorganic material (organic resin material) (such as polyimide or acrylic)or a siloxane material may also be used. It is to be noted that asiloxane material corresponds to a resin including a Si—O—Si bond.Siloxane has a skeleton structure of a bond of silicon (Si) and oxygen(O). As for a substituent, an organic group containing at least hydrogen(such as an alkyl group or an aryl group) is used. As for a substituent,a fluoro group may also be used. Further, as for a substituent, a fluorogroup and an organic group containing at least hydrogen may also beused. Further, a material having a low-wettability surface can furtherreduce wettability by plasma treatment or the like.

In this embodiment mode, the conductive layer (insulating layer) isformed with the use of a droplet discharging unit. The dropletdischarging unit is a generic term for a unit for discharging a droplet,such as a nozzle having a discharging outlet for discharging thecomposition or a head equipped with one or more nozzles. The nozzle ofthe droplet discharging unit has a diameter of 0.02 to 100 μm(preferably less than or equal to 30 μm), and the amount of thecomposition to be discharged from the nozzle is in the range of 0.001 to100 pl (preferably greater than or equal to 0.1 pl and less than orequal to 40 pl, much preferably less than or equal to 10 pl). The amountof the discharged composition increases in proportion to the diameter ofthe nozzle. The distance between an object to be processed and thedroplet discharging outlet of the nozzle is preferably as small aspossible in order to discharge the composition at a desired position,for example, about 0.1 to 3 mm (preferably less than or equal to 1 mm).

As the composition to be discharged from the droplet discharging outlet,a material in which a conductive material is dissolved or dispersed in asolvent is used. The conductive material corresponds to a microparticleor a dispersive nanoparticle of one or a plurality of kinds of metalsuch as Ag, Au, Cu, Ni, Pt, Pd, Ir, Rh, W, and Al. In addition,microparticles or dispersive nanoparticles of one or a plurality ofkinds of a metal sulfide of Cd, or Zn, an oxide of Fe, Ti, Ge, Si, Zr,Ba, or the like, and silver halide may be mixed to the above conductivematerial. Moreover, as a conductive material, titanium nitride, indiumtin oxide (ITO), indium tin oxide containing silicon oxide (ITSO),organic indium, organic tin, or zinc oxide, which is used as atransparent conductive film, or the like may be used. The conductivematerial may be mixed with a particle of one or a plurality of kinds ofthe elements. However, in consideration of a specific resistance value,it is preferable to use a solvent in which gold, silver, or copper isdissolved or dispersed for the composition to be discharged from thedischarging outlet. It is much preferable to use silver or copper, whichhas lower resistance. When silver or copper is used, a barrier film maybe provided as a countermeasure against impurities. As the barrier film,a silicon nitride film or a film of nickel boron (NiB) can be used.

In addition, a particle with a plurality of layers, in which aconductive material is coated with another conductive material, may alsobe used. For example, a particle with a three-layer structure in whichcopper is coated with nickel boron (NiB) and the nickel boron is furthercoated with silver, or the like may be used. As for the solvent, esterssuch as butyl acetate or ethyl acetate, alcohols such as isopropylalcohol or ethyl alcohol, an organic solvent such as methyl ethyl ketoneor acetone, or water is used. The viscosity of the composition ispreferably less than or equal to 20 mPa·s, which prevents thecomposition from drying when being discharged and enables thecomposition to be discharged smoothly from the discharging outlet. Thesurface tension of the composition is preferably less than or equal to40 mN/m. It is to be noted that the viscosity of the composition and thelike may be appropriately controlled depending on a solvent to be usedor an intended purpose. For example, the viscosity of a composition inwhich ITO, organic indium, or organic tin is dissolved or dispersed in asolvent may be set to be 5 to 20 mPa·s, the viscosity of a compositionin which silver is dissolved or dispersed in a solvent may be set to be5 to 20 mPa·s, and the viscosity of a composition in which gold isdissolved or dispersed in a solvent may be set to be 5 to 20 mPa·s.

Further, the conductive layer may also be formed of a plurality ofstacked conductive materials. In addition, the conductive layer may beformed first by a droplet discharging method using silver as aconductive material and may be then plated with copper or the like. Theplating may be performed by electroplating or a chemical (electroless)plating method. The plating may be performed by immersing a substratesurface in a container filled with a solution containing a platingmaterial; alternatively, the solution containing a plating material maybe applied to the substrate placed obliquely (or vertically) so as toflow the solution containing a plating material on the substratesurface. When the plating is performed so that the solution is appliedto the substrate placed obliquely, there is an advantage of downsizingan apparatus which is used for the process of a large substrate.

The diameter of a particle of the conductive material is preferablysmall for the purpose. of preventing nozzles from being clogged and formanufacturing a minute pattern, although it depends on the diameter ofeach nozzle, a desired shape of a pattern, or the like. Preferably, thediameter of the particle of the conductive material is less than orequal to 0.1 μm. The composition is formed by various methods such as anelectrolyzing method, an atomizing method, and a wet reduction method,and the particle size is generally about 0.01 to 10 μm. When a gasevaporation method is employed, the size of nanoparticles protected by adispersant is as minute as about 7 nm, and when the surface of eachparticle is covered with a coating, the nanoparticles do not aggregatein the solvent and are stably dispersed in the solvent at roomtemperature, and behave similarly to liquid. Accordingly, it ispreferable to use a coating.

In addition, the step of discharging the composition may be performedunder reduced pressure. After the composition is discharged, eitherdrying or baking or both of them is/are performed. Both the drying stepand baking step are heat treatment, and for example, drying is performedat 100° C. for 3 minutes and baking is performed at 200 to 550° C. for15 to 60 minutes, and they are different in purpose, temperature, andtime period. The steps of drying and baking are performed under normalpressure or reduced pressure by laser beam irradiation, rapid thermalannealing, heating using a heating furnace, or the like. It is to benoted that the timing and the number of such heat treatment is notparticularly limited. The substrate may be heated in advance tofavorably perform the steps of drying and baking, and the temperature atthat time is, although it depends on the material of the substrate orthe like, generally 100 to 800° C. (preferably, 200 to 550° C.). Throughthese steps, the solvent in the composition is volatilized or thedispersant is chemically removed, and furthermore, nanoparticles aremade in contact with each other and fusion and welding are acceleratedsince a peripheral resin is hardened and shrunk.

A continuous wave or pulsed gas laser or solid-state laser may be usedfor laser beam irradiation. An excimer laser, a YAG laser, or the likecan be used as the former gas laser. A laser using a crystal of YAG,YVO₄, GdVO₄, or the like which is doped with Cr, Nd, or the like can beused as the latter solid-state laser. It is preferable to use acontinuous wave laser in consideration of the absorptance of a laserbeam. Moreover, a laser beam irradiation method in which pulsed andcontinuous wave lasers are combined may be used. It is preferable thatthe heat treatment by laser beam irradiation be instantaneouslyperformed within several microseconds to several tens of seconds so asnot to damage the substrate, depending on heat resistance of thesubstrate. Rapid thermal annealing (RTA) is carried out by raising thetemperature rapidly and heating the substrate instantaneously forseveral microseconds to several minutes with the use of an infrared lampor a halogen lamp which emits ultraviolet to infrared light in an inertgas atmosphere. Since this treatment is performed instantaneously, onlyan outermost thin film can be heated and the film in the lower layer isnot adversely affected. In other words, even a substrate having low heatresistance such as a plastic substrate is not adversely affected.

After the conductive layer or the like is formed by discharging acomposition by a droplet discharging method, the surface thereof may beplanarized by pressing with pressure to enhance a level of planarity. Asa pressing method, concavity and convexity may be planarized and reducedby scanning the surface with a roller-shaped object, or the surface maybe pressed perpendicularly by a flat plate-shaped object. A heating stepmay be performed at the time of pressing. Alternatively, the concavityand convexity of the surface may be removed with an air knife after thesurface is softened or melted with a solvent or the like. A CMP methodmay also be used for polishing the surface. This step can be employed inplanarizing a surface when concavity and convexity are generated by adroplet discharging method.

This embodiment mode shows an example in which a conductive layer isformed in accordance with the present invention. However, when amaterial contained in a liquid composition to be discharged is aninsulating material or a semiconductor material, an insulating layer, asemiconductor layer, or the like can also be formed in accordance withthe present invention.

In accordance with the present invention, a component such as a wiringincluded in a display device can be formed into a desired shape. Inaddition, since complicated photolithography steps can be reduced and adisplay device can be manufactured through a simplified process, loss ofmaterials and the cost can be reduced. Therefore, a high performance andhighly reliable display device can be manufactured with a high yield.

Embodiment Mode 2

In this embodiment mode, a method for forming a contact hole through amore simplified process at low cost will be described with reference toFIGS. 4A to 4D.

When conductive layers are electrically connected with an insulatinglayer interposed therebetween, an opening (so-called contact hole) isformed in the insulating layer. In this case, a mask layer is not formedover the insulating layer, and the opening is selectively formed bylaser beam irradiation. A first conductive layer is formed, aninsulating layer is stacked over the first conductive layer, and aregion where the opening is formed in the stacked first conductive layerand insulating layer is selectively irradiated with a laser beam fromthe insulating layer side. The laser beam is transmitted through theinsulating layer and absorbed by the first conductive layer. The firstconductive layer is heated by energy of the absorbed laser beam andevaporated, and the insulating layer that is stacked thereover isbroken. Therefore, the opening is formed in the first conductive layerand the insulating layer, and part of the conductive layer below theinsulating layer is exposed on the side wall and the bottom (or only onthe side wall) of the opening. By formation of a second conductive layerin the opening so as to be in contact with the exposed first conductivelayer, the first and second conductive layers can be electricallyconnected to each other with the insulating layer interposedtherebetween. In other words, in the present invention, the conductivelayer is irradiated with a laser beam, an irradiated region of theconductive layer with a laser beam is evaporated by laser ablation, andthe opening is formed in the insulating layer that is formed over theconductive layer.

The above method for forming a contact hole will be specificallydescribed with reference to FIGS. 4A to 4D. In this embodiment mode, asshown in FIGS. 4A to 4D, conductive layers 721 a and 721 b, and aninsulating layer 722 are formed over a substrate 720.

The conductive layers 721 a and 721 b are formed to have a stackedstructure. In this embodiment mode, low-melting point metal (chromium inthis embodiment mode) that is relatively easily evaporated is used forthe conductive layer 721 b, and refractory metal (tungsten in thisembodiment mode) that is not easily evaporated compared to theconductive layer 721 b is used for the conductive layer 721 a.

As shown in FIG. 4B, the conductive layers 721 a and 721 b (anirradiated region 724) are selectively irradiated with a laser beam 723from the insulating layer 722 side, and the irradiated region of theconductive layer 721 b is evaporated by irradiation energy. Theinsulating layer 722 over the irradiated region of the conductive layer721 b is removed, and an opening 725 can be formed. The conductive layer721 b is separated into conductive layers 728 a and 728 b, and theinsulating layer 722 is separated into insulating layers 727 a and 727 b(refer to FIG. 4C). A conductive layer 726 is formed in the opening 725where the conductive layers 721 a and 721 b are exposed; therefore, theconductive layer 721 a, the conductive layer 721 b, and the conductivelayer 726 can be electrically connected (refer to FIG. 4D).

A laser beam writing system for irradiating a processing region with alaser beam will be described with reference to FIG. 31. A laser beamdirect writing system is used in this embodiment mode, and a processingregion is directly irradiated with a laser beam. As shown in FIG. 31, alaser beam direct writing system 1001 includes: a personal computer(hereinafter, referred to as a PC) 1002 for carrying out various kindsof controls upon irradiation with a laser beam; a laser oscillator 1003for outputting a laser beam; a power source 1004 of the laser oscillator1003; an optical system (an ND filter) 1005 for attenuating a laserbeam; an acousto-optic modulator (AOM) 1006 for modulating the intensityof a laser beam; an optical system 1007 including a lens for enlargingor reducing a cross section of a laser beam, a mirror for changing alight path, and the like; a substrate moving unit 1009 having an X stageand a Y stage; a D/A converter 1010 for converting control data outputfrom the PC from digital to analog data; a driver 1011 for controllingthe acousto-optic modulator 1006 depending on an analog voltage outputfrom the D/A converter; and a driver 1012 outputting a driving signalfor driving the substrate moving unit 1009.

As the laser oscillator 1003, a laser oscillator that is capable ofemitting ultraviolet light, visible light, or infrared light can beused. The following laser oscillators can be used: an excimer laseroscillator such as KrF, ArF, XeCl, or Xe; a gas laser oscillator such asHe, He—Cd, Ar, He—Ne, or HF; a solid-state laser oscillator using acrystal such as YAC; GdVO₄, YVO₄, YLF, or YAlO₃ doped with Cr, Nd, Er,Ho, Ce, Co, Ti, or Tm; and a semiconductor laser oscillator such as GaN,GaAs, GaAlAs, or InGaAsP. In the case of the solid-state laseroscillator, first to fifth harmonics of fundamental waves are preferablyused. In order to adjust the shape or path of a laser beam emitted fromthe laser oscillator, an optical system including a shutter, a reflectorsuch as a mirror or a half mirror, a cylindrical lens, a convex lens,and the like may be provided.

Next, treatment for modifying quality of a film using the laser beamdirect writing system will be described. When a substrate 1008 is put onthe substrate moving unit 1009, the PC 1002 detects a position of amarker that is marked on the substrate with the use of a camera (notshown). The PC 1002 generates data for moving the substrate moving unit1009 based on the positional data of the detected marker and data for awriting pattern that has been previously input in the PC. When theamount of output light for the acousto-optic modulator 1006 iscontrolled through the driver 1011 by the PC 1002, laser beam outputfrom the laser oscillator 1003 is attenuated by the optical system 1005,so that the amount of light is adjusted to a predetermined amount in theacousto-optic modulator 1006. The light path and beam shape of the laserbeam output from the acousto-optic modulator 1006 are changed in theoptical system 1007. The laser beam is condensed by the lens, and a basefilm formed over the substrate is irradiated with the condensed laserbeam, whereby the treatment for modifying quality of the base film isperformed. At this time, the substrate moving unit 1009 is controlled tomove in an X direction and a Y direction in accordance with the data formoving the substrate moving unit that is generated by the PC 1002. As aresult, a predetermined portion is irradiated with the laser beam, sothat treatment for modifying the quality of the film is performed.

The shorter the wavelength of the laser beam is, the shorter the beamcan be condensed in diameter. Therefore, in order to process a regionwith a minute width, a short wavelength laser beam is preferably used.

The spot shape of the laser beam on the film surface is processed tohave a dotted, circular, elliptic, rectangular, or linear (exactly, anarrow rectangular) shape by the optical system.

FIG. 31 shows an example of the system in which a front surface of thesubstrate is irradiated with a laser beam to be exposed. Alternatively,another laser beam writing system in which a back surface of thesubstrate is irradiated with a laser beam to be exposed may be used byarbitrarily changing the optical system and the substrate moving unit.

Here, the substrate is selectively irradiated with the laser beam bybeing moved; however, the present invention is not limited thereto.Irradiation with the laser beam can be performed by scanning of thelaser beam in the X axis and Y axis directions. In this case, a polygonmirror or a galvanometer mirror is preferably used for the opticalsystem 1007.

The conductive layers 721 a and 721 b can be formed by an evaporationmethod, a sputtering method, a PVD (Physical Vapor Deposition) method, aCVD method such as a low-pressure CVD (LPCVD) method or a plasma CVDmethod, or the like. In addition, a method by which a component can beformed into a desired pattern by transferring or drawing, for example,various printing methods (a method for forming a component into adesired pattern, such as screen (mimeograph) printing, offset(planograph) printing, relief printing, gravure (intaglio) printing, andthe like), a dispenser method, a selective-coating method, or the likecan also be used. As the conductive layers 721 a and 721 b, one or aplurality of chromium, molybdenum, nickel, titanium, cobalt, copper, andaluminum can be used.

In FIGS. 4A to 4D, an example is shown, in which the conductive layer721 b is evaporated by irradiation with the laser beam 723, the opening725 is formed in the insulating layer 722, and the stacked conductivelayer 721 a remains. FIGS. 5A to 5D show other examples in which anopening is formed to reach a conductive layer formed below an insulatinglayer.

FIG. 5A shows an example in which only an upper portion of an upperconductive layer of conductive layers which are stacked below aninsulating layer is removed by laser ablation. Conductive layers 731 and732, and an insulating layer 733 are provided over a substrate 730, anda conductive layer 734 is provided in an opening 750 formed in theconductive layer 732 and the insulating layer 733. In the opening 750,the conductive layer 732 is exposed and electrically connected to and incontact with the conductive layer 734.

The conductive layer below the insulating layer may be a stacked layerincluding a plurality of kinds of conductive layers with differentmelting points, or of course, may be a single layer. FIGS. 5B and 5Cshow examples in which a conductive layer below an insulating layer is asingle layer. FIG. 5B is an example in which only an upper portion of aconductive layer below an insulating layer is removed by laser ablation.FIG. 5C is an example in which a conductive layer in a portion below aninsulating layer is removed by laser ablation until a substrate 740 isexposed.

In FIG. 5B, a conductive layer 736 and an insulating layer 738 areprovided over a substrate 735, and a conductive layer 739 is provided inan opening 751 formed in the conductive layer 736 and the insulatinglayer 738. In the opening 751, the conductive layer 736 is exposed andis electrically connected to and in contact with the conductive layer739. As shown in FIG. 5B, when only the upper portion of the conductivelayer is partially removed in a thickness direction, laser beamirradiation conditions (such as energy or irradiation time) may becontrolled, or the conductive layer 736 may be formed thickly.

In FIG. 5C, conductive layers 741 a and 741 b, and an insulating layer743 are provided over a substrate 740, and a conductive layer 744 isprovided in an opening 752 formed in the conductive layers 741 a and 741b and the insulating layer 743. In the opening 752, the conductivelayers 741 a and 741 b are exposed and electrically connected to and incontact with the conductive layer 744. It is not always necessary thatthe upper conductive layer and the lower conductive layer are in contactwith each other at the bottom of the opening as shown in FIG. 5B, and astructure in which the upper conductive layer is formed to be in contactwith and electrically connected to the lower conductive layer exposed onthe side surface of the opening may be employed.

Further, as for the shape of the opening functioning as a contact hole,the side surface does not need to be perpendicular to the bottomsurface, and the side of the opening may be tapered as shown in FIG. 5D.In FIG. 5D, conductive layers 746 and 747, and an insulating layer 748are formed over a substrate 745, and an opening 753 is formed in theinsulating layer 748 and the conductive layer 747. The opening 753 has amortar shape and the side surface of the opening 753 is tapered withrespect to the bottom surface. A conductive layer 749 is provided in anopening 753.

As described above, in the opening provided in the insulating layer, thelower conductive layer below the insulating layer and the upperconductive layer over the insulating layer are electrically connected toeach other. In this embodiment mode, a second conductive layer is formedof metal with a high sublimation property over a first conductive layer,and the second conductive layer is evaporated by a laser beam, wherebyan opening is formed in an insulating layer formed over the first andsecond conductive layers. The size and shape of the opening formed inthe insulating layer and the conductive layer can be controlled by laserbeam irradiation conditions (such as laser intensity and irradiationtime) and characteristics of materials for the insulating layer and theconductive layer (such as thermal conductivity, melting point, andboiling point). FIGS. 35A to 35D show an example of the size of thelaser beam spot and the size of the formed opening.

Over a substrate 300, a first conductive layer 301 a (301 a 1, 301 a 2,and 301 a 3) and a second conductive layer 301 b are stacked, and aninsulating layer 302 is formed so as to cover the first conductive layer301 a (301 a 1, 301 a 2, and 301 a 3) and the second conductive layer301 b. In FIGS. 35A to 35D, the first conductive layer 301 a (301 a 1,301 a 2, and 301 a 3) has a stacked layer structure including aplurality of thin films. For example, titanium can be used for the firstconductive layer 301 a 1, aluminum can be used for the first conductivelayer 301 a 2, titanium can be used for the first conductive layer 301 a3, and chromium can be used for the second conductive layer 301 b. Inaddition, tungsten, molybdenum, or the like may also be used for thefirst conductive layer 301 a 3. Of course, the second conductive layer301 b can also have a stacked layer structure, and a stacked layerincluding copper and chromium or the like can be used.

The insulating layer 302 and the second conductive layer 301 b areirradiated with a laser beam 303 having a diameter L1, so that anirradiated region 304 is selectively formed in the insulating layer 302and the second conductive layer 301 b. As the energy of the laser beam303 is higher, the second conductive layer 301 b receives higher energyand heat is transmitted to the irradiated region and also to theperipheral portion in the second conductive layer 301 b as shown in FIG.35C. Therefore, in the second conductive layer 301 b, an opening havinga diameter L2 that is larger than the diameter L18 of the laser beam 303is formed, and the opening is also formed in the insulating layer 302formed over the conductive layer 301 b. As described above, the secondconductive layer 301 b is separated into second conductive layers 308 aand 308 b, and the insulating layer 302 is separated into insulatinglayers 307 a and 307 b, and an opening 305 is formed. A conductive film306 is formed in the opening 305 where the first conductive layer 301 a3 is exposed and electrically connected to the first conductive layer301 a (301 a 1, 301 a 2, and 301 a 3) and the second conductive layers308 a and 308 b (refer to FIG. 35D).

The size of the opening with respect to the size of the irradiatedregion determined by the diameter of the laser beam depends on an energylevel of the laser beam, and when the energy of the laser beam is highenough to evaporate the second conductive layer, the energy istransmitted also to the periphery of the irradiated region and thesecond conductive layer is evaporated; therefore, the opening that islarger than the irradiated region with the laser beam is formed in thesecond conductive layer. On the other hand, when the energy of the laserbeam is low, an opening with almost the same size as that of theirradiated region is formed in the second conductive layer. In addition,when the second conductive layer is formed using a sublimation metalmaterial with high thermal conductivity, energy of a laser beam can beeasily transmitted; therefore, an opening that is larger than theirradiated region can be formed.

As described above, by control of the energy of the laser beam, theevaporation range of the second conductive layer which is irradiatedwith a laser beam can be controlled; thus, the size of the openingformed in the second conductive layer and the insulating layer can beappropriately controlled.

After the opening is formed by laser beam irradiation, a conductivematerial and an insulating material remaining around the opening (aresidue in a portion where the conductive layer and the insulating layerare removed) can be washed with a liquid so that the residue is removed.In this case, a non-reactive substance such as water may be used forwashing, or a chemical solution such as an etchant which reacts with(dissolves) the insulating layer may be used. With an etchant, theopening is over-etched, and dusts and the like are removed, so that thesurface is more planarized. Further, the opening can also be widened.

Since the opening can be selectively formed by a laser beam, a masklayer does not need to be formed, and the steps and the materials can bereduced. In addition, there are advantages that a conductive layer andan insulating layer to be processed can be formed into a predeterminedshape with high precision since the laser beam can be condensed into avery small spot, and the regions other than the processing region do notneed to be heated substantially since heating is performed in a shorttime by the laser beam.

As described above, an opening (contact hole) which electricallyconnects conductive layers can be formed in an insulating layer by laserbeam irradiation without implementing a complicated photolithographystep and forming a mask layer.

Accordingly, when a display device is manufactured in accordance withthe present invention, the process can be simplified, and loss ofmaterials and the cost can be reduced. Therefore, a display device canbe manufactured with a high yield.

Embodiment Mode 3

FIG. 25A is a top view showing a structure of a display panel inaccordance with the present invention. A pixel portion 2701 in whichpixels 2702 are arranged in a matrix, a scanning line input terminal2703, and a signal line input terminal 2704 are formed over a substrate2700 having an insulating surface. The number of pixels may bedetermined in accordance with various standards. In the case of XGA ofRGB full color display, the number of pixels may be 1024×768×3 (RGB). Inthe case of UXGA of RGB full color display, the number of pixels may be1600×1200×3 (RGB), and in the case of full-spec high-definition RGB fullcolor display, the number of pixels may be 1920×1080×3 (RGB).

The pixels 2702 are arranged in a matrix by intersection of scanninglines extended from the scanning line input terminal 2703 and signallines extended from the signal line input terminal 2704. Each pixel 2702is provided with a switching element and a pixel electrode connected tothe switching element. A typical example of the switching element is aTFT. The gate electrode side of the TFT is connected to a scanning line,and a source or drain side of the TFT is connected to a signal line,which enables each pixel to be independently controlled by a signalinput from an external portion.

FIG. 25A shows a structure of a display panel in which a signal to beinput to a scanning line and a signal line is controlled by an externaldriver circuit. Alternatively, a driver IC 2751 may be mounted on asubstrate 2700 by a COG (Chip on Glass) method as shown in FIG. 26A. Asanother mounting mode, a TAB (Tape Automated Bonding) method may also beused as shown in FIG. 26B. The driver IC may be formed over a singlecrystal semiconductor substrate or may be formed over a glass substratewith a TFT. In FIGS. 26A and 26B, the driver IC 2751 is connected to anFPC 2750.

When a TFT provided in a pixel is formed of a polycrystalline(microcrystalline) semiconductor having high crystallinity, a scanningline driver circuit 3702 can also be formed over a substrate 3700 asshown in FIG. 25B. In FIG. 25B, reference numeral 3701 denotes a pixelportion, reference numeral 3704 denotes a signal line input terminal anda signal line driver circuit is controlled by an external driver circuitas in FIG. 25A. When a TFT in a pixel 4701 is formed of apolycrystalline (microcrystalline) semiconductor or a single crystalsemiconductor having high mobility like a TFT formed in the presentinvention, a pixel portion 4701, a scanning line driver circuit 4702,and a signal line driver circuit 4704 can be formed to be integratedover a glass substrate 4700 as shown in FIG. 25C.

An embodiment mode of the present invention will be described withreference to FIGS. 7A to 14B. More specifically, a method formanufacturing a display device including a reverse staggered thin filmtransistor to which the present invention is applied will be described.FIGS. 7A, 8A, 9A, 10A, 11A, 12A, and 13A are top views of a pixelportion of a display device, FIGS. 7B, 8B, 9B, 10B, 11B, 12B, and 13Bare cross-sectional views taken along lines A-C in FIGS. 7A, 8A, 9A,10A, 11A, 12A, and 13A, and FIGS. 7C, 8C, 9C, 10C, 11C, 12C, and 13C arecross-sectional views taken along lines B-D in FIGS. 7A, 8A, 9A, 10A,11A, 12A, and 13A. FIGS. 14A and 14B are also cross-sectional views of adisplay device.

As a substrate 100, a glass substrate made of barium borosilicate glass,aluminoborosilicate glass, or the like; a quartz substrate; a metalsubstrate; or a plastic substrate having heat resistance that canwithstand process temperature of the present manufacturing process isused. The surface of the substrate 100 may be polished by a CMP methodor the like so as to be planarized. An insulating layer may be formedover the substrate 100. The insulating layer may be formed to have asingle layer or stacked layer structure using an oxide materialcontaining silicon or a nitride material containing silicon by variousmethods such as a CVD method, a plasma CVD method, a sputtering method,and a spin coating method. This insulating layer is not necessarilyformed; however, this insulating layer has an advantageous effect ofblocking contamination substances and the like from the substrate 100.

A conductive film is formed over the substrate 100. The conductive filmcan be formed by a sputtering method, a PVD (Physical Vapor Deposition)method, a CVD (Chemical Vapor Deposition) method such as a low-pressureCVD (LPCVD) method or a plasma CVD method, or the like. The conductivefilm may be formed using an element such as Ag, Au, Ni, Pt, Pd, Ir, Rh,Ta, W, Ti, Mo, Al, or Cu, or an alloy material or compound materialcontaining the above element as its main component. In addition, asemiconductor film typified by a polycrystalline silicon film doped withan impurity element such as phosphorus, or an AgPdCu alloy may be used.In addition, a single layer structure or a structure including aplurality of layers may be used, and for example, a two-layer structureof a tungsten nitride (WN) film and a molybdenum (Mo) film or athree-layer structure in which a tungsten film with a thickness of 50nm, an alloy film of aluminum and silicon (Al—Si) with a thickness of500 nm, and a titanium nitride film with a thickness of 30 nm aresequentially stacked may be used. In the case of the three-layerstructure, tungsten nitride may be used in place of tungsten of a firstconductive film, an alloy film of aluminum and titanium (Al—Ti) may beused in place of the alloy film of aluminum and silicon (Al—Si) of asecond conductive film, and a titanium film may be used in place of thetitanium nitride film of a third conductive film.

In this embodiment mode, a gate electrode layer is formed by selectivelydischarging a composition. By such selective formation of the gateelectrode layer, the process can be simplified.

This embodiment mode has a feature that a method for discharging acomposition from a discharging outlet of a droplet discharging apparatusis varied depending on the size and shape of a region where a conductivelayer is formed. A gate electrode layer 104 (104 a and 104 b)corresponding to a gate wiring which is formed in a relatively wide areais formed by continuously discharging compositions from dropletdischarging apparatuses 136 a and 136 b without stop as shown in FIG.7B. On the other hand, a gate electrode layer 105 (105 a and 105 b)which is formed in a relatively small area is formed by drippingcompositions from droplet discharging apparatuses 137 a and 137 b asshown in FIG. 7B and 7C. In such a manner, a method for discharging aliquid composition may be varied depending on a pattern to be formed.

The gate electrode layer 104 (104 a and 104 b) and the gate electrodelayer 105 (105 a and 105 b) may be formed of an element such as Ag, Au,Ni, Pt, Pd, Ir, Rh, Ta, W, Ti, Mo, Al, or Cu, or an alloy material orcompound material containing the element as its main component. Amixture of the elements may also be used. Not only a single layerstructure but also a stacked layer structure including two or morelayers may also be used.

When the gate electrode layer 104 (104 a and 104 b) and the gateelectrode layer 105 (105 a and 105 b) need to be processed, a mask layermay be formed and etching may be performed by dry etching or wetetching. An ICP (Inductively Coupled Plasma) etching method may be used,and etching conditions (the amount of electric power applied to acoil-shaped electrode, the amount of electric power applied to anelectrode on a substrate side, the electrode temperature on thesubstrate side, and the like) may be appropriately adjusted, and theelectrode layer may be etched into a tapered shape. It is to be notedthat, as an etching gas, a chlorine-based gas typified by Cl₂, BCl₃,SiCl₄, or CCL₄, a fluorine-based gas typified by CF₄, SF₆, or NF₃, or O₂can be appropriately used.

As a mask layer, a resin material such as an epoxy resin, a phenolresin, a novolac resin, an acrylic resin, a melamine resin, or aurethane resin is used. Moreover, the mask layer is formed by a dropletdischarging method using an organic material such as benzocyclobutene,parylene, fluorinated arylene ether, or polyimide having alight-transmitting property; a compound material formed bypolymerization of a siloxane-based polymer or the like; a compositionmaterial containing water-soluble homopolymer and water-solublecopolymer; or the like. Alternatively, a commercial resist materialcontaining photosensitizer may be used. For example, a novolac resin anda naphthoquinonediazide compound that is a photosensitizer, which aretypical positive type resists; a base resin, diphenylsilanediol, and anacid generation agent, which are negative type resists; or the like maybe used. In using any material, the surface tension and the viscosity ofa material are appropriately adjusted by adjusting the concentration ofa solvent or by adding a surfactant or the like.

Next, a gate insulating layer 106 is formed over the gate electrodelayers 104 a, 104 b, 105 a, and 105 b. The gate insulating layer 106 maybe formed of an oxide material of silicon, a nitride material ofsilicon, or the like, and a single layer or stacked layer structure maybe used. In this embodiment mode, a two-layer structure of a siliconnitride film and a silicon oxide film is used. In addition, a singlelayer of a silicon oxynitride film or a stacked layer including three ormore layers may be used. Preferably, a silicon nitride film having densefilm quality is used. When silver, copper, or the like is used for aconductive layer formed by a droplet discharging method, by formation ofa silicon nitride film or an NiB film as a barrier film thereover, aneffect that diffusion of an impurity is prevented and the surface isplanarized can be obtained. In order to form a dense insulating filmwith less gate leak current at low deposition temperature, a reactiongas containing a rare gas element such as argon may be mixed into aninsulating film to be formed.

Next, a semiconductor layer is formed. A semiconductor layer having oneconductivity type may be formed as needed. In addition, an NMOSstructure of an n-channel TFT in which a semiconductor layer havingn-type conductivity is formed, a PMOS structure of a p-channel TFT inwhich a semiconductor layer having p-type conductivity is formed, or aCMOS structure of an n-channel TFT and a p-channel TFT can bemanufactured. In order to impart conductivity, an element impartingconductivity may be added to the semiconductor layer by doping to forman impurity region in the semiconductor layer, so that an n-channel TFTand a p-channel TFT can be formed. Instead of formation of thesemiconductor layer having n-type conductivity, plasma treatment with aPH₃ gas may be performed, so that conductivity is imparted to thesemiconductor layer.

A material for forming the semiconductor layer can be an amorphoussemiconductor (hereinafter also referred to as “AS”) formed by a vapordeposition method using a semiconductor material gas typified by silaneor germane or a sputtering method, a polycrystalline semiconductorformed by crystallizing the amorphous semiconductor using light energyor thermal energy, a semi-amorphous semiconductor (also referred to asmicrocrystal and hereinafter also referred to as “SAS”), or the like.The semiconductor layer can be formed by various methods (a sputteringmethod, an LPCVD method, a plasma CVD method, and the like).

An SAS is a semiconductor having an intermediate structure betweenamorphous and crystalline (including single crystal and polycrystalline)structures and a third state which is stable in free energy. Moreover,an SAS includes a crystalline region with a short-distance order andlattice distortion. A crystal grain having a diameter of 0.5 to 20 nmcan be observed at least in a portion of a film. In a case where siliconis contained as a main component, Raman spectrum is shifted to the lowwave number side that is lower than 520 cm⁻¹. The diffraction peaks of(111) and (220), which are believed to be derived from silicon crystallattice, are observed by X-ray diffraction. An SAS contains hydrogen orhalogen by at least 1 atomic % or more for terminating dangling bonds.An SAS is formed by glow discharge decomposition (plasma CVD) of a gascontaining silicon. As the gas containing silicon, SiH₄ can be used, andin addition, Si₂H₆, SiH₂Cl₂, SiHCl₃, SiC₄, SiF₄, and the like can alsobe used. Further, F₂ and GeF₄ may be mixed. The gas containing siliconmay be diluted with H₂, or H₂ and one or a plurality of kinds of raregas elements of He, Ar, Kr, and Ne. The dilution ratio is 1:2 to 1:1000,pressure is approximately 0.1 to 133 Pa, and a power source frequency is1 to 120 MHz, preferably, 13 to 60 MHz. A temperature for heating thesubstrate is preferably less than or equal to 300° C., and an SAS canalso be formed at 100 to 200° C. It is preferable that the concentrationof impurities of atmospheric components such as oxygen, nitrogen, andcarbon as impurity elements in the film be less than or equal to 1×10²⁰cm⁻³. In particular, an oxygen concentration is preferably less than orequal to 5×10¹⁹ cm⁻³, and much preferably, less than or equal to 1×10¹⁹cm⁻³. Further, when a rare gas element such as helium, argon, krypton,or neon is contained to further increase the lattice distortion,stability can be enhanced, and a favorable SAS can be obtained. Further,as the semiconductor layer, an SAS layer formed by using ahydrogen-based gas may be stacked over an SAS layer formed by using afluorine-based gas.

As an example of a typical amorphous semiconductor, hydrogenatedamorphous silicon can be given while polysilicon or the like can begiven as an example of a typical crystalline semiconductor. Polysilicon(polycrystalline silicon) includes so-called high-temperaturepolysilicon formed using polysilicon which is formed at processingtemperatures of greater than or equal to 800° C. as a main material,so-called low-temperature polysilicon formed using polysilicon which isformed at processing temperatures of less than or equal to 600° C. as amain material, polysilicon crystallized by adding an element whichpromotes crystallization, and the like. Of course, as described above, asemi-amorphous semiconductor or a semiconductor which includes acrystalline phase in a portion thereof can also be used.

When a crystalline semiconductor layer is used for the semiconductorlayer, the crystalline semiconductor layer may be formed by variousmethods such as a laser crystallization method, a thermalcrystallization method, and a thermal crystallization method using anelement such as nickel which promotes crystallization. Further, amicrocrystalline semiconductor that is an SAS may be crystallized bylaser irradiation to enhance crystallinity. In a case where an elementwhich promotes crystallization is not used, before the amorphous siliconfilm is irradiated with a laser beam, the amorphous silicon film isheated at 500° C. for one hour in a nitrogen atmosphere to dischargehydrogen so that a hydrogen concentration in the amorphous silicon filmbecomes less than or equal to 1×10²⁰ atoms/cm³. This is because, if theamorphous silicon film contains much hydrogen, the amorphous siliconfilm may be broken by laser beam irradiation.

A method for introducing a metal element into the amorphoussemiconductor layer is not particularly limited as long as it is amethod for introducing the metal element to a surface of or inside theamorphous semiconductor layer. For example, a sputtering method, a CVDmethod, a plasma treatment method (including a plasma CVD method), anadsorption method, or a method for applying a solution of metal salt canbe used. Among them, a method using a solution is simple andadvantageous in that the concentration of the metal element can beeasily controlled. At this time, it is desirable to form an oxide filmby UV light irradiation in an oxygen atmosphere, a thermal oxidationmethod, treatment with ozone water containing hydroxyl radical orhydrogen peroxide, or the like to improve wettability of the surface ofthe amorphous semiconductor layer so that an aqueous solution isdiffused on the entire surface of the amorphous semiconductor layer.

In order to crystallize the amorphous semiconductor layer, heattreatment may be combined with crystallization by laser beamirradiation, or one of heat treatment and laser beam irradiation may becarried out multiple times.

Moreover, the crystalline semiconductor layer may be directly formedover the substrate by a plasma method. Furthermore, the crystallinesemiconductor layer may be selectively formed over the substrate by alinear plasma method.

The semiconductor layer may be formed of an organic semiconductormaterial by a printing method, a dispenser method, a spray method, aspin coating method, a droplet discharging method, or the like. In thiscase, since the etching step is not necessary, the number of steps canbe reduced. As the organic semiconductor, a low-molecular material suchas pentacene, a high-molecular material, or the like can be used. Inaddition, an organic dye, a conductive high-molecular material, or thelike can also be used. As the organic semiconductor material used in thepresent invention, a n-electron conjugated high-molecular material ofwhich skeleton includes a conjugated double bond is desirable.Typically, a soluble high-molecular material such as polythiophene,polyfluorene, poly(3-alkylthiophene), or a polythiophene derivative canbe used.

In addition, as the organic semiconductor material which can be used inthe present invention, there is a material which can be formed byforming a soluble precursor of the material and then performing aprocess thereon. The organic semiconductor material through a precursorincludes polythienylenevinylene, poly(2,5-thienylenevinylene),polyacetylene, polyacetylene derivatives, polyallylenevinylene, and thelike.

The precursor is changed into the organic semiconductor not only by heattreatment but also by addition of a reaction catalyst such as a hydrogenchloride gas. Moreover, as a typical solvent for dissolving the solubleorganic semiconductor material, toluene, xylene, chlorobenzene,dichlorobenzene, anisole, chloroform, dichloromethane, γbutyllactone,butylcellosolve, cyclohexane, N-methyl-2-pyrrolidone (NMP),cyclohexanone, 2-butanon, dioxane, dimethylformamide (DMF),tetrahydrofuran (THF), and the like can be used.

A semiconductor film 107 and a semiconductor film 108 having oneconductivity type are formed over the gate insulating layer 106. In thisembodiment mode, amorphous semiconductor layers are formed as thesemiconductor film 107 and the semiconductor film 108 having oneconductivity type. In this embodiment mode, a semiconductor film havingn-type conductivity containing phosphorus (P) that is an impurityelement imparting n-type conductivity is formed as the semiconductorfilm having one conductivity type. The semiconductor film having oneconductivity type functions as a source region and a drain region. Thesemiconductor film having one conductivity type may be formed as needed,and a semiconductor film having n-type conductivity containing animpurity element imparting n-type conductivity (P, As) or asemiconductor film having p-type conductivity containing an impurityelement imparting p-type conductivity (B) can be formed.

Similarly to the gate electrode layers 104 and 105, the semiconductorfilm 107 and the semiconductor film 108 having one conductivity type areformed into a desired shape with the use of a mask layer. A compositioncontaining a material for forming the mask layer is discharged to thesemiconductor film 107 and the semiconductor film 108 having oneconductivity type by droplet discharging apparatuses 110 a and 110 b,whereby mask layers 109 a and 109 b are selectively formed (refer toFIGS. 8A to 8C).

The semiconductor film 107 and the semiconductor film 108 having oneconductivity type are processed with the use of the mask layers 109 aand 109 b, whereby semiconductor layers 111 a and 111 b, andsemiconductor layers 112 a and 112 b having one conductivity type areformed.

A mask layer is formed of an insulator such as resist or polyimide by adroplet discharging method. An opening 114 is formed in part of the gateinsulating layer 106 by etching with the use of the mask layer, and partof the gate electrode layer 105 provided below the gate insulating layer106 is exposed. Either plasma etching (dry etching) or wet etching maybe employed to etch the gate insulating layer 106; however, plasmaetching is suitable to process a large substrate. As the etching gas, afluorine-based gas such as CF₄ or NF₃ or chlorine-based gas such as Cl₂or BCl₃ is used. An inert gas such as He or Ar may be added to theetching gas appropriately. When an etching process using atmosphericdischarge plasma is employed, a local discharging process is alsopossible, and the mask layer does not need to be formed over the entiresurface of the substrate.

Further, as shown in Embodiment Mode 2, the opening 114 may also beformed by a laser beam. The gate electrode layer 105 is selectivelyirradiated with a laser beam from the gate insulating layer 106 side,whereby part of an irradiated region of the gate electrode layer 105 isevaporated by irradiation energy. The gate insulating layer 106 over theirradiated region of the gate electrode layer 105 is removed, and theopening 114 can be formed. A source electrode layer or drain electrodelayer 121 is formed in the opening 114 where the gate electrode layer105 is exposed, and the gate electrode layer 105 and the sourceelectrode layer or drain electrode layer 121 can be electricallyconnected to each other. Part of the source electrode layer or drainelectrode layer forms a capacitor.

In this embodiment mode, the source electrode layer or drain electrodelayer is formed by selectively discharging a composition. When thesource electrode layer or drain electrode layer is selectively formed,the process can be simplified.

This embodiment mode has a feature that a method for discharging acomposition from a discharging outlet of a droplet discharging apparatusis varied depending on the size and shape of a region where the sourceelectrode layer or drain electrode layer is formed. Source electrodelayers or drain electrode layers 120 and 122 corresponding to sourcewirings or drain wirings formed in a relatively wide area are formed bycontinuously discharging compositions without stop from dropletdischarging apparatuses 116 a and 116 b as shown in FIGS. 9B and 9C. Onthe other hand, source electrode layers or drain electrode layers 121and 123 formed in a relatively small area are formed by drippingcompositions intermittently from droplet discharging apparatuses 117 aand 117 b as shown in FIGS. 9B and 9C. As described above, a method fordischarging a liquid composition may be varied depending on the patternto be formed.

As a conductive material for forming the source electrode layer or drainelectrode layer 120, the source electrode layer or drain electrode layer121, the source electrode layer or drain electrode layer 122, and thesource electrode layer or drain electrode layer 123, a compositioncontaining a particle of a metal such as Ag (silver), Au (gold), Cu(copper), W (tungsten), or Al (aluminum) as its main component can beused. Moreover, titanium nitride, indium tin oxide (ITO), indium tinoxide containing silicon oxide (ITSO), organic indium, organic tin, orzinc oxide, having a light-transmitting property, or the like may becombined.

In addition, by combination with a droplet discharging method, loss ofmaterials and the cost can be reduced, as compared to formation over theentire surface by a spin coating method or the like. In accordance withthe present invention, even when wirings and the like are arranged in adense and complicated manner due to downsizing and thinning, the wiringsand the like can be stably formed with good adhesion.

Further, in this embodiment mode, when the source electrode layer ordrain electrode layer is formed into a desired shape by a dropletdischarging method, regions having different wettability may be formedin a region where the source electrode layer or drain electrode layer isformed and a peripheral portion thereof as pre-treatment. In the presentinvention, when components such as a conductive layer, an insulatinglayer, and a mask layer are formed by discharging a droplet by a dropletdischarging method, a region having low wettability and a region havinghigh wettability with respect to a material for forming the componentsare formed in the formation region of the components, whereby the shapeof the components can be controlled. By such treatment, there areregions with different wettability in the formation region; therefore,droplets remain only in the region having high wettability, and thecomponents with a desired pattern can be formed with highcontrollability. This step can be used as pre-treatment for anycomponent (such as an insulating layer, a conductive layer, a masklayer, or a wiring layer) when a liquid material is used.

The source electrode layer or drain electrode layer 120 also functionsas a source wiring layer, and the source electrode layer or drainelectrode layer 122 also functions as a power source line. After thesource electrode layers or drain electrode layers 120, 121, 122, and 123are formed, the semiconductor layers 111 a and 111 b, and thesemiconductor layers 112 a and 112 b having one conductivity type areformed into a desired shape. In this embodiment mode, the semiconductorlayers 111 a and 111 b, and the semiconductor layers 112 a and 112 bhaving one conductivity type are processed by etching using the sourceelectrode layers or drain electrode layers 120, 121, 122, and 123 asmasks, whereby semiconductor layers 118 a and 118 b, and semiconductorlayers 119 a, 119 b, 119 c and 119 d having one conductivity type areformed.

Through the above process, transistors 124 a and 124 b which are reversestaggered transistors are formed (refer to FIGS. 10A to 10C).

Next, an insulating layer 126 is formed over the gate insulating layer106, and the transistors 124 a and 124 b. As the insulating layer 126,an inorganic material (such as silicon oxide, silicon nitride, siliconoxynitride, or silicon nitride oxide), a photosensitive ornonphotosensitive organic material (an organic resin material such aspolyimide, acrylic, polyamide, polyimide amide, resist, orbenzocyclobutene), a film formed of one or a plurality of kinds oflow-dielectric constant materials, a stacked layer structure thereof,and the like can be used. Alternatively, a siloxane material may also beused.

An opening 125 is formed in the insulating layer 126. In this embodimentmode, as shown in Embodiment Mode 2, the opening 125 is formed using alaser beam. The source electrode layer or drain electrode layer 123 isselectively irradiated with a laser beam from the insulating layer 126side, whereby part of an irradiated region of the source electrode layeror drain electrode layer 123 is evaporated by irradiation energy. Theinsulating layer 126 over the irradiated region of the source electrodelayer or drain electrode layer 123 is removed, and the opening 125 canbe formed. A first electrode layer is formed in the opening 125 wherethe source electrode layer or drain electrode layer 123 is exposed, andthe source electrode layer or drain electrode layer 123 and the firstelectrode layer can be electrically connected to each other.

A composition containing a conductive material is selectively dischargedto the insulating layer 126 to form the first electrode layer. Whenlight is emitted from the substrate 100 side, the first electrode layermay be formed by the steps of forming a predetermined pattern using acomposition containing indium tin oxide (ITO), indium tin oxidecontaining silicon oxide (ITSO), indium zinc oxide containing zinc oxide(ZnO) (IZO (indium zinc oxide)), zinc oxide (ZnO), ZnO doped withgallium (Ga), tin oxide (SnO₂), or the like and baking the composition.

In this embodiment mode, the first electrode layer is formed byselectively discharging a composition. In such a manner, when the firstelectrode layer is selectively formed, the process can be simplified.

In this embodiment mode, the first electrode layer is formed through atleast two steps. In this embodiment mode, the first electrode layer isformed using a first conductive layer and a second conductive layer.When the first electrode layer is formed, a first liquid compositioncontaining a conductive material is applied on the outer side of apattern that is desired to be formed (corresponding to a contour or anedge portion of the pattern), and a first conductive layer having aframe-shape is formed. As shown in FIGS. 11A to 11C, a first conductivelayer 127 (127 a and 127 b) having a frame-shape is formed over theinsulating layer 126 by droplet discharging apparatuses 128 a and 128 b.

It is preferable that the first conductive layer be a closed region likea frame. Next, a second liquid composition containing a conductivematerial is applied so that the space inside the first conductive layerhaving a frame-shape is filled, whereby a second electrode layer isformed. As shown in FIGS. 12A to 12C, a second conductive layer 129 isformed by a droplet discharging apparatus 130 inside the frame formed ofthe first conductive layer 127 over the insulating layer 126. The firstconductive layer 127 and the second conductive layer 129 are formed tobe in contact with each other, and the first conductive layer 127 isformed to surround the second conductive layer 129; therefore, the firstconductive layer 127 and the second conductive layer 129 can be used asa first electrode layer 134 that is continuous (refer to FIGS. 13A to13C).

When a conductive layer or the like is formed using a liquidcomposition, a shape of a conductive layer to be formed is greatlyinfluenced by the viscosity of a composition, drying conditions insolidification (such as temperature or pressure), wettability withrespect to a formation region, and the like. Therefore, with lowviscosity or high wattability with respect to a formation region, aliquid composition spreads over a region where a conductive layer or thelike is formed. On the other hand, with high viscosity or lowwettability with respect to a formation region, there is a problem inthat space (also referred to as pin holes) and unevenness are formed inor on the surface of the conductive layer and a level of planarity isdecreased.

Therefore, in the present invention, when the first conductive layerwhich determines a contour of a region where the conductive layer isformed is formed by applying a composition with relatively highviscosity and low wettability with respect to a formation region, a sideedge portion which becomes a contour of a desired pattern can be formedwith high controllability. When a liquid composition with low viscosityand high wettability with respect to a formation region is appliedinside a frame formed of the first conductive layer, space, unevenness,and the like due to bubbles and the like formed in or on the surface ofthe conductive layer are reduced, and the conductive layer which is veryflat and uniform can be formed. Therefore, by separate formation of anouter-side conductive layer and an inner-side conductive layer, aconductive layer that has a high level of planarity, less defects, and adesired pattern can be formed with high controllability.

The first electrode layer 134 may be cleaned or polished by a CMP methodor with the use of a polyvinyl alcohol based porous material, so thatthe surface thereof is planarized. In addition, after polishing using aCMP method, ultraviolet light irradiation, oxygen plasma treatment, orthe like may be performed on the surface of the first electrode layer134.

Through the above process, a TFT substrate for a display panel in whicha bottom-gate TFT and the first electrode layer 134 are connected toeach other over the substrate 100 is completed. The TFT in thisembodiment mode is reverse staggered type.

Next, an insulating layer 131 (also called a partition wall) isselectively formed. The insulating layer 131 is formed so as to have anopening over the first electrode layer 134. In this embodiment mode, theinsulating layer 131 is formed over the entire surface and patterned byetching with the use of a mask such as resist. When the insulating layer131 is formed by a droplet discharging method, a printing method, adispenser method, or the like by which the pattern can be formeddirectly and selectively, the patterning by etching does not need to becarried out.

The insulating layer 131 can be formed using an inorganic insulatingmaterial such as silicon oxide, silicon nitride, silicon oxynitride,aluminum oxide, aluminum nitride, or aluminum oxynitride; an acrylicacid, a methacrylic acid, or a derivative thereof; a heat-resistanthigh-molecular material such as polyimide, aromatic polyamide, orpolybenzimidazole; an insulating material of inorganic siloxane whichincludes a Si—O—Si bond among compounds which are formed using asiloxane-based material as a starting material and which includesilicon, oxygen, and hydrogen; or an insulating material of organicsiloxane of which hydrogen bonded to silicon is substituted by anorganic group such as methyl or phenyl. A photosensitive ornonphotosensitive material such as acrylic or polyimide may also beused. It is preferable that the insulating layer 131 be formed to have acontinuously-changing radius of curvature, because the coverage by anelectroluminescent layer 132 and a second electrode layer 133 to beformed over the insulating layer 131 improves.

After the insulating layer 131 is formed by discharging a composition bya droplet-discharging method, a surface thereof may be planarized bypressing with pressure to enhance a level of planarity. As a pressingmethod, concavity and convexity of the surface may be reduced byscanning the surface by a roller-shaped object, or the surface may bepressed perpendicularly by a flat plate-shaped object. Alternatively,concavity and convexity of the surface may be removed with an air knifeafter the surface is softened or melted with a solvent or the like. ACMP method may also be used for polishing the surface. This step can beemployed in planarizing the surface when the surface becomes uneven by adroplet-discharging method. When a level of planarity is enhanced bythis step, irregular display of the display panel can be prevented, andthus, a high precision image can be displayed.

A light-emitting element is formed over the substrate 100 that is a TFTsubstrate for the display panel (refer to FIGS. 14A and 14B).

Before an electroluminescent layer 132 is formed, heat treatment iscarried out at 200° C. in the atmospheric pressure to remove moisture inthe first electrode layer 134 and the insulating layer 131 or moistureadsorbed on their surfaces. It is preferable to carry out the heattreatment at 200 to 400° C., much preferably 250 to 350° C., under lowpressure and to form the electroluminescent layer 132 successivelywithout exposing the substrate to the air by a vacuum evaporation methodor a droplet discharging method under low pressure.

As the electroluminescent layer 132, materials emitting light of red(R), green (G), and blue (B) are selectively formed by an evaporationmethod or the like using evaporation masks. The materials emitting lightof red (R), green (G), and blue (B) can also be formed by a dropletdischarging method similarly to a color filter (such as a low-molecularmaterial or a high-molecular material), and thus, materials for R, G.and B can be selectively formed without using masks, which ispreferable. A second electrode layer 133 is formed over theelectroluminescent layer 132, and a display device having a displayfunction using a light-emitting element is completed.

Although not shown in the drawings, it is effective to provide apassivation film so as to cover the second electrode layer 133. Apassivation (protection) film provided in manufacturing a display devicemay have a single layer structure or a multilayer structure. Thepassivation film can be formed using an insulating film containingsilicon nitride (SiN), silcon oxide (SiO₂), silicon oxynitride (SiON),silicon nitride oxide (SiNO), aluminum nitride (AlN), aluminumoxynitride (AlON), aluminum nitride oxide containing more nitrogen thanoxygen (AlNO), aluminum oxide, diamond-like carbon (DLC), orcarbon-containing nitrogen (CN_(x)) with a single-layer structure or astacked layer structure. For example, a stacked layer such as acarbon-containing nitrogen (CN_(x)) film and silicon nitride (SiN) film,or an organic material can also be used, and a stacked layer of a highmolecular material such as styrene polymer may also be used.Alternatively, a siloxane material may also be used.

At this time, it is preferable to use a film by which favorable coverageis provided as the passivation film, and it is effective to use a carbonfilm, particularly, a DLC film for the passivation film. A DLC film canbe formed in the temperature range from room temperature to less than orequal to 100° C.; therefore, it can also be formed easily over theelectroluminescent layer with low heat resistance. A DLC film can beformed by a plasma CVD method (typically, an RF plasma CVD method, amicrowave CVD method, an electron cyclotron resonance (ECR) CVD method,a heat filament CVD method, or the like), a combustion method, asputtering method, an ion beam evaporation method, a laser evaporationmethod, or the like. As a reaction gas for deposition, a hydrogen gasand a hydrocarbon-based gas (for example, CH₄, C₂H₂, C₆H₆, and the like)are used to be ionized by glow discharge, and the ions are acceleratedto impact against a cathode to which negative self-bias voltage isapplied. Further, a CN film may be formed with the use of a C₂H₄ gas anda N₂ gas as a reaction gas. A DLC film has high blocking effect againstoxygen; therefore, oxidization of the electroluminescent layer can besuppressed. Accordingly, a problem such as oxidation of theelectroluminescent layer during a sealing step that is performed latercan be prevented.

A sealing material is formed over the substrate 100 having an element,and the substrate 100 having the element is sealed using a sealingsubstrate. Thereafter, a flexible wiring board may be connected to agate wiring layer that is formed to be electrically connected to thegate electrode layer 104, so that electrical connection to an externalportion is obtained. This is also applied to a source wiring layer thatis formed to be electrically connected to the source electrode layer ordrain electrode layer 120 that is also a source wiring layer.

A filler is filled and sealed between the substrate 100 having theelement and the sealing substrate. A dripping method can also be usedinstead of filling and sealing the filler. Instead of the filler, aninert gas such as nitrogen may also be filled. In addition, when adrying agent is provided in the display device, deterioration due tomoisture in the light-emitting element can be prevented. The dryingagent may be provided on the sealing substrate side or the substrate 100side having the element. Alternatively, a concave portion may be formedin a region where the sealing material is formed in the substrate, andthe drying agent may be provided there. Further, when the drying agentis provided in a place corresponding to a region which does notcontribute to display such as a driver circuit region or a wiring regionof the sealing substrate, an aperture ratio is not decreased even if thedrying agent is an opaque substance. The filler may contain ahygroscopic material so as to have a function as a drying agent. Asdescribed above, a display device having a display function using alight-emitting element is completed.

In this embodiment mode, the switching TFT has a single gate structure,but may have a multi-gate structure such as a double gate structure.When the semiconductor layer is formed of SAS or a crystallinesemiconductor, an impurity region can be formed by addition of animpurity imparting one conductivity type. In this case, thesemiconductor layer may have impurity regions with differentconcentrations. For example, a low-concentration impurity region may beprovided around a channel region and a region overlapping with the gateelectrode layer, and a high-concentration impurity region may beprovided in a region on the outer side of the low-concentration impurityregion.

This embodiment mode can be appropriately combined with Embodiment Mode1 or 2.

In accordance with the present invention, a component such as a wiringincluded in a display device can be formed into a desired shape. Inaddition, since complicated photolithography steps can be reduced and adisplay device can be manufactured through a simplified process, loss ofmaterials and the cost can be reduced. Therefore, a high performance andhighly reliable display device can be manufactured with a high yield.

Embodiment Mode 4

In this embodiment mode, an example of a highly reliable display devicewhich is manufactured through a simplified process at low cost will bedescribed. More specifically, a light-emitting display device using alight-emitting element as a display element will be described. A methodfor manufacturing a display device of this embodiment mode will bedescribed with reference to FIGS. 15A and 15B.

As a base film over a substrate 150 having an insulating surface, a basefilm 151 a is formed using a silicon nitride oxide film with a thicknessof 10 to 200 nm (preferably, 50 to 150 nm), and a base film 151 b isformed using a silicon oxynitride film with a thickness of 50 to 200 nm(preferably, 100 to 150 nm) by a sputtering method, a PVD (PhysicalVapor Deposition) method, or a CVD (Chemical Vapor Deposition) methodsuch as a low pressure CVD (LPCVD) method or a plasma CVD method.Alternatively, it is also possible to use an acrylic acid, a methacrylicacid, or a derivative thereof; a heat-resistant high-molecular materialsuch as polyimide, aromatic polyamide, or polybenzimidazole; or asiloxane resin. Further, other resin materials such as a vinyl resin,e.g. polyvinyl alcohol or polyvinyl butyral, an epoxy rein, a phenolresin, a novolac resin, an acrylic rein, a melamine resin, and aurethane resin can be used. In addition, it is also possible to use anorganic material such as benzocyclobutene, parylene, fluorinated aryleneether, or polyimide, or a composition material containing water-solublehomopolymers and water-soluble copolymers. Further, an oxazole resinsuch as photo-curing polybenzoxazole can also be used.

Further, a droplet discharging method, a printing method (a method bywhich a pattern can be formed, such as screen printing or offsetprinting), a coating method such as a spin coating method, a dippingmethod, a dispenser method, or the like can also be used. In thisembodiment mode, the base films 151 a and 151 b are formed by a plasmaCVD method. As the substrate 150, a glass substrate, a quartz substrate,a silicon substrate, a metal substrate, or a stainless steel substratehaving an insulating film formed on its surface may be used.Alternatively, a plastic substrate having heat resistance which canwithstand the processing temperature in this embodiment mode, or aflexible substrate such as a film may also be used. As a plasticsubstrate, a substrate made of PET (polyethylene terephthalate), PEN(polyethylene naphthalate), or PES (polyethersulfone) can be used. As aflexible substrate, a synthetic resin such as acrylic can be used. Sincea display device manufactured in this embodiment mode has a structure inwhich light is extracted from the light-emitting element through thesubstrate 150, the substrate 150 needs to have a light-transmittingproperty.

As the base film, silicon oxide, silicon nitride, silicon oxynitride,silicon nitride oxide, or the like can be used, and either a singlelayer structure or a stacked layer structure including two or threelayers can be employed.

Next, a semiconductor film is formed over the base film. Thesemiconductor film may be formed with a thickness of 25 to 200 nm(preferably, 30 to 150 nm) by various methods (such as a sputteringmethod, an LPCVD method, and a plasma CVD method). In this embodimentmode, it is preferable to use a crystalline semiconductor layer which isobtained by crystallizing an amorphous semiconductor film by laserirradiation.

The semiconductor film obtained as described above may be doped with asmall amount of an impurity element (boron or phosphorus) in order tocontrol the threshold voltage of thin film transistors. Such doping withthe impurity element may be performed before the crystallization step ofthe amorphous semiconductor film. When the amorphous semiconductor filmis doped with an impurity element and then subjected to heat treatmentto be crystallized, activation of the impurity element can also beperformed. In addition, defects caused in doping can be recovered.

Then, the crystalline semiconductor film is patterned by etching into adesired shape, whereby a semiconductor layer is formed.

An etching process for patterning the semiconductor film into a desiredshape may employ either plasma etching (dry etching) or wet etching. Ina case of processing a large substrate, plasma etching is suitable. Asan etching gas, a fluorine-based gas such as CF₄ or NF₃ or achlorine-based gas such as Cl₂ or BCl₃ is used, to which an inert gassuch as He or Ar may be appropriately added. When an etching processusing atmospheric discharge plasma is employed, local dischargingprocess is also possible, and the mask layer does not need to be formedover the entire surface of the substrate.

In the present invention, a conductive layer for forming a wiring layeror an electrode layer, a mask layer for forming a predetermined pattern,or the like may also be formed by a method by which a pattern can beselectively formed, such as a droplet discharging method. By a dropletdischarging betting) method (also called an ink jet method depending onits system), a predetermined pattern (such as a conductive layer or aninsulating layer) can be formed by selectively discharging (jetting) adroplet of a composition which is mixed for a particular purpose. Atthis time, treatment to control wettablity or adhesion may be carriedout to a formation region. In addition, a method by which a pattern canbe transferred or drawn, for example, a printing method (a method forforming a pattern, such as screen printing or offset printing), adispenser method, or the like can also be used. In this embodiment mode,a gate electrode layer, a semiconductor layer, a source electrode layer,a drain electrode layer, and the like can be formed using a conductivelayer and a semiconductor layer which are formed selectively andprecisely in a plurality of steps by a droplet discharging method or thelike as in Embodiment Mode 1. Therefore, the process can be simplified,and loss of materials can be prevented; therefore, the cost can bereduced.

In this embodiment mode, as a mask, a resin material such as an epoxyresin, an acrylic resin, a phenol resin, a novolac resin, a melamineresin, or a urethane resin is used. Alternatively, an organic materialsuch as benzocyclobutene, parylene, fluorinated arylene ether, orpolyimide having a light transmitting property; a compound materialformed by polymerization of siloxane-based polymers or the like; acomposition material containing a water-soluble homopolymer and awater-soluble copolymer; and the like can also be used. Furtheralternatively, a commercially available resist material containing aphotosensitiser may also be used. For example, a novolac resin and anaphthoquinonediazide compound that is a photosensitizer, which aretypical positive type resists; a base resin, diphenylsilanediol, and anacid generation agent, which are negative type resists; or the like maybe used. A droplet discharging method is used with any material, and thesurface tension and the viscosity of a material are appropriatelyadjusted by adjusting the concentration of a solvent or by adding asurfactant or the like.

A gate insulating layer covering the semiconductor layer is formed. Thegate insulating layer is formed using an insulating film containingsilicon with a thickness of 10 to 150 nm by a plasma CVD method, asputtering method, or the like. The gate insulating layer may be formedusing a known material such as an oxide material or a nitride materialof silicon, typified by silicon nitride, silicon oxide, siliconoxynitride, and silicon nitride oxide, and may be a stacked layer or asingle layer. For example, the insulating layer may be a stacked layerof three layers including a silicon nitride film, a silicon oxide film,and a silicon nitride film, or a single layer or a stacked layer of twolayers of a silicon oxynitride film.

Next, a gate electrode layer is formed over the gate insulating layer.The gate electrode layer can be formed by a sputtering method, anevaporation method, a CVD method, or the like. The gate electrode layermay be formed using an element such as tantalum (Ta), tungsten (W),titanium (Ti), molybdenum (Mo), aluminum (Al), copper (Cu), chromium(Cr), or neodymium (Nd), or an alloy material or a compound materialcontaining these elements as its main component. Further, as the gateelectrode layer, a semiconductor film typified by a polycrystallinesilicon film doped with an impurity element such as phosphorus, orAgPdCu alloy may be used. In addition, the gate electrode layer may be asingle layer or a stacked layer.

In this embodiment mode, the gate electrode layer is formed into atapered shape; however, the present invention is not limited thereto.The gate electrode layer may have a stacked layer structure, where onlyone layer has a tapered shape while the other has a perpendicular sidesurface by anisotropic etching. The taper angles may be differentbetween the stacked gate electrode layers as in this embodiment mode, orthe taper angles may be the same. With the tapered shape, coverage by afilm that is stacked thereover is improved and defects are reduced,whereby reliability is enhanced.

The gate insulating layer may be etched to some extent and reduced inthickness (so-called film decrease) by the etching step for forming thegate electrode layer.

An impurity element is added to the semiconductor layer to form animpurity region. The impurity region can be formed as ahigh-concentration impurity region and a low-concentration impurityregion through the control of the concentration of the impurity element.A thin film transistor having a low-concentration impurity region isreferred to as a thin film transistor having an LDD (Light doped drain)structure. In addition, the low-concentration impurity region can beformed so as to overlap with the gate electrode. Such a thin filmtransistor is referred to as a thin film transistor having a GOLD (GateOverlapped LDD) structure. The polarity of the thin film transistor ismade n-type through addition of phosphorus (P) or the like to animpurity region thereof. In a case where a p-type thin film transistoris formed, boron (B) or the like may be added.

In this embodiment mode, a region of the impurity region, which overlapswith the gate electrode layer with the gate insulating layer interposedtherebetween, is denoted as a Lov region. Further, a region of theimpurity region, which does not overlap with the gate electrode layerwith the gate insulating layer interposed therebetween, is denoted as aLoff region. In FIG. 15B, the impurity regions are shown by hatching anda blank space. This does not mean that the blank space is not doped withan impurity element, but makes it easy to understand that theconcentration distribution of the impurity element in these regionsreflects the mask and the doping condition. It is to be noted that thisis the same in other drawings of this specification.

In order to activate the impurity element, heat treatment, strong lightirradiation, or laser beam irradiation may be performed. At the sametime as the activation, plasma damage to the gate insulating layer andplasma damage to the interface between the gate insulating layer and thesemiconductor layer can be recovered.

Next, a first interlayer insulating layer which covers the gateelectrode layer and the gate insulating layer 157 is formed. In thisembodiment mode, a stacked layer structure of insulating films 167 and168 is employed. As the insulating films 167 and 168, a silicon nitridefilm, a silicon nitride oxide film, a silicon oxynitride film, a siliconoxide film, or the like can be formed by a sputtering method or a plasmaCVD method. Alternatively, other insulating films containing silicon mayalso be used as a single layer or a stacked layer structure includingthree or more layers.

Further, heat treatment is performed at 300 to 550° C. for 1 to 12 hoursin a nitrogen atmosphere, and the semiconductor layer is hydrogenated.Preferably, this heat treatment is performed at 400 to 500° C. Throughthis step, dangling bonds in the semiconductor layer are terminated byhydrogen contained in the insulating film 167 that is an interlayerinsulating layer. In this embodiment mode, heat treatment is performedat 410° C.

The insulating films 167 and 168 can also be formed using a material ofaluminum nitride (AlN), aluminum oxynitride (AlON), aluminum nitrideoxide containing more nitrogen than oxygen (AlNO), aluminum oxide,diamond-like carbon (DLC), nitrogen-containing carbon (CN),polysilazane, or other substances containing an inorganic insulatingmaterial. A material containing siloxane may also be used. Further, anorganic insulating material such as polyimide, acrylic, polyamide,polyimide amide, resist, or benzocyclobutene may also be used. Inaddition, an oxazole resin can be used, and for example, photo-curabletype polybenzoxazole or the like can be used.

Next, a contact hole (opening), which reaches the semiconductor layer,is formed in the insulating films 167 and 168, and the gate insulatinglayer with the use of a mask formed of a resist. A conductive film isformed so as to cover the opening, and the conductive film is etched,whereby a source electrode layer or drain electrode layer is formed,which is electrically connected to part of a source region or drainregion. In order to form the source electrode layer or drain electrodelayer, a conductive film is formed by a PVD method, a CVD method, anevaporation method, or the like, and the conductive film is etched intoa desired shape. Further, the conductive film can be selectively formedin a predetermined place by a droplet discharging method, a printingmethod, a dispenser method, an electrolytic plating method, or the like.A reflow method or a damascene method may also be used. The sourceelectrode layer or drain electrode layer is formed using a metal such asAg, Au, Cu, Ni, Pt, Pd, Ir, Rh, W, Al, Ta, Mo, Cd, Zn, Fe, Ti, Si, Ge,Zr, or Ba, or alloy or nitride thereof. In addition, a stacked layerstructure of these materials may also be used.

In this embodiment mode, the gate electrode layer, the semiconductorlayer, the source electrode layer, the drain electrode layer, the wiringlayer, the first electrode layer, and the like included in the displaydevice may be formed by discharging a liquid composition containing amaterial for forming the above components in a plurality of steps asshown in Embodiment Mode 1. As shown in Embodiment Mode 1, a firstconductive layer having a frame-shape is formed along the contour of thepattern of the conductive layer by a first discharging step, and asecond conductive layer is formed so as to fill inside the frame formedof the first conductive layer by a second discharging step.

Therefore, when the first conductive layer (insulating layer) whichdetermines the contour of a formation region of the conductive layer(insulating layer) is formed by applying a composition with relativelyhigh viscosity and low wettability with respect to the formation region,a side edge portion which becomes a contour of a desired pattern can beformed with high controllability. When a liquid composition with lowviscosity and high wettability with respect to the formation region isapplied inside a frame formed of the first conductive layer (insulatinglayer), space, unevenness, and the like due to bubbles and the like inor on the surface of the conductive layer are reduced, and a conductivelayer (insulating layer) which is very flat and uniform can be formed.Therefore, by separate formation of an outer-side conductive layer(insulating layer) and an inner-side conductive layer (insulatinglayer), a conductive layer (insulating layer) that has a high level ofplanarity, less defects, and a desired pattern can be formed with highcontrollability.

Through the above steps, an active matrix substrate can be manufactured,in which a p-channel thin film transistor 285 having a p-type impurityregion in a Lov region and an n-channel thin film transistor 275 havingan n-channel impurity region in a Lov region are provided in aperipheral driver circuit region 204; and a multi-channel type n-channelthin film transistor 265 having an n-type impurity region in a Loffregion and a p-channel thin film transistor 255 having a p-type impurityregion in a Lov region are provided in a pixel region 206.

The structure of the thin film transistor in the pixel region is notlimited to this embodiment mode, and a single gate structure in whichone channel formation region is formed, a double gate structure in whichtwo channel formation regions are formed, or a triple gate structure inwhich three channel formation regions are formed may be employed.Further, the thin film transistor in the peripheral driver circuitregion may also employ a single gate structure, a double gate structure,or a triple gate structure.

Next, an insulating film 181 is formed as a second interlayer insulatinglayer. In FIGS. 15A and 15B, a separation region 201 for separation byscribing, an external terminal connection region 202 to which an FPC isattached, a wiring region 203 that is a lead wiring region for theperipheral portion, the peripheral driver circuit region 204, and thepixel region 206 are provided. Wirings 179 a and 179 b are provided inthe wiring region 203, and a terminal electrode layer 178 connected toan external terminal is provided in the external terminal connectionregion 202.

The insulating film 181 can be formed using a material of silicon oxide,silicone nitride, silicon oxynitride, silicon nitride oxide, aluminumnitride (AlN), aluminum oxide containing nitrogen (also referred to asaluminum oxynitride) (AlON), aluminum nitride containing oxygen (alsoreferred to as aluminum nitride oxide) (AlNO), aluminum oxide,diamond-like carbon (DLC), nitrogen-containing carbon (CN), PSG(phosphorus glass), BPSG (boron phosphorus glass), alumina, or othersubstances containing an inorganic insulating material. In addition, asiloxane resin may also be used. Further, a photosensitive ornon-photosensitive organic insulating material such as polyimide,acrylic, polyamide, polyimide amide, resist, benzocyclobutene,polysilazane, or a low-dielectric constant material (Low-k material) canalso be used. In addition, an oxazole resin can be used, and forexample, photo-curable type polybenzoxazole or the like can be used. Aninterlayer insulating layer provided for planarization is required tohave high heat resistance, a high insulating property, and a high levelof planarity. Thus, the insulating film 181 is preferably formed by acoating method typified by a spin coating method.

The insulating film 181 can be formed by a dipping method, spraycoating, a doctor knife, a roll coater, a curtain coater, a knifecoater, a CVD method, an evaporation method, or the like. The insulatingfilm 181 may also be formed by a droplet discharging method. In the caseof a droplet discharging method, a material solution can be saved. Inaddition, a method by which a pattern can be transferred or drawn, likea droplet discharging method, for example, a printing method (a methodfor forming a pattern, such as screen printing or offset printing), adispenser method, or the like can also be used.

A minute opening, that is, a contact hole is formed in the insulatingfilm 181 in the pixel region 206. The source electrode layer or drainelectrode layer is electrically connected to a first electrode layer 185through the opening formed in the insulating film 181. The openingformed in the insulating film 181 can be formed by irradiation with alaser beam as shown in Embodiment Mode 2. In this embodiment mode, thesource electrode layer or drain electrode layer is formed using alow-melting point metal that is relatively easily evaporated (chromiumin this embodiment mode). The source electrode layer or drain electrodelayer is selectively irradiated with a laser beam from the insulatingfilm 181 side, whereby part of an irradiated region of the sourceelectrode layer or drain electrode layer is evaporated by irradiationenergy. The insulating film 181 over the irradiated region of the sourceelectrode layer or drain electrode layer is removed, and the opening canbe formed. The first electrode layer 185 is formed in the opening wherethe source electrode layer or drain electrode layer is exposed, and thesource electrode layer or drain electrode layer and the first electrodelayer 185 can be electrically connected to each other.

The first electrode layer 185 functions as an anode or a cathode, andmay be formed using an element such as Ti, Ni, W, Cr, Pt, Zn, Sn, In, orMo; an alloy material or a compound material containing the aboveelements as its main component such as TiN, TiSi_(X)N_(Y), WSi_(X),WN_(X), WSi_(X)N_(Y), or NbN; or a stacked film thereof with a totalthickness of 100 to 800 nm.

In this embodiment mode, a light-emitting element is used as a displayelement, and the first electrode layer 185 has a light-transmittingproperty because light from the light-emitting element is extracted fromthe first electrode layer 185 side. The first electrode layer 185 isformed using a transparent conductive film which is etched into adesired shape.

In the present invention, the first electrode layer 185 that is alight-transmitting electrode layer may be specifically formed using atransparent conductive film formed of a light-transmitting conductivematerial, and indium oxide containing tungsten oxide, indium zinc oxidecontaining tungsten oxide, indium oxide containing titanium oxide,indium tin oxide containing titanium oxide, or the like can be used. Ofcourse, indium tin oxide (ITO), indium zinc oxide (IZO), indium tinoxide doped with silicon oxide (ITSO), or the like can also be used.

In addition, even in the case of a non-light-transmitting material suchas a metal film, when the thickness is made thin (preferably, about 5 to30 nm) so as to be able to transmit light, light can be emitted from thefirst electrode layer 185. As a metal thin film that can be used for thefirst electrode layer 185, a conductive film formed of titanium,tungsten, nickel, gold, platinum, silver, aluminum, magnesium, calcium,lithium, or alloy thereof, or the like can be used.

The first electrode layer 185 can be formed by an evaporation method, asputtering method, a CVD method, a printing method, a dispenser method,a droplet discharging method, or the like. In this embodiment mode, thefirst electrode layer 185 is formed by a sputtering method using indiumzinc oxide containing tungsten oxide. The first electrode layer 185 ispreferably formed with a total thickness of 100 to 800 nm.

The first electrode layer 185 may be cleaned or polished by a CMP methodor with the use of a polyvinyl alcohol based porous material, so thatthe surface thereof is planarized. In addition, after polishing using aCMP method, ultraviolet light irradiation, oxygen plasma treatment, orthe like may be performed on the surface of the first electrode layer185.

Heat treatment may be performed after the first electrode layer 185 isformed. By the heat treatment, moisture contained in the first electrodelayer 185 is discharged. Accordingly, degasification or the like is notcaused in the first electrode layer 185. Thus, even when alight-emitting material that is easily deteriorated by moisture isformed over the first electrode layer, the light-emitting material isnot deteriorated; therefore, a highly reliable display device can bemanufactured.

Next, an insulating layer 186 (also referred to as a partition wall or abarrier) is formed to cover the edge of the first electrode layer 185and the source electrode layer or drain electrode layer.

The insulating layer 186 can be formed using silicon oxide, siliconnitride, silicon oxynitride, silicon nitride oxide, or the like, and mayhave a single layer structure or a stacked layer structure including twoor three layers. In addition, as other materials for the insulatinglayer 186, a material of aluminum nitride, aluminum oxynitridecontaining more oxygen than nitrogen, aluminum nitride oxide containingmore nitrogen than oxygen, aluminum oxide, diamond-like carbon (DLC),nitrogen-containing carbon, polysilazane, or other substances containingan inorganic insulating material can be used. A material containingsiloxane may also be used. Further, a photosensitive ornon-photosensitive organic insulating material such as polyimide,acrylic, polyamide, polyimide amide, resist, benzocyclobutene, orpolysilazane, can also be used. In addition, an oxazole resin can beused, and for example, photo-curable type polybenzoxazole or the likecan be used.

The insulating layer 186 can be formed by a sputtering method, a PVD(Physical Vapor deposition) method, a CVD method such as a low-pressureCVD (LPCVD) method or a plasma CVD method, a droplet discharging methodby which a pattern can be selectively formed, a printing method by whicha pattern can be transferred or drawn (a method for forming a patternsuch as screen printing or offset printing), a dispenser method, acoating method such as a spin coating method, or a dipping method.

An etching process for forming a desired shape may employ either plasmaetching (dry etching) or wet etching. In the case where a largesubstrate is processed, plasma etching is more suitable. As an etchinggas, a fluorine based gas such as CF₄ or NF₃, or a chlorine based gassuch as Cl₂, or BCl₃ is used, to which an inert gas such as He or Ar maybe appropriately added. When an etching process using atmosphericdischarge plasma is employed, a local discharging process is alsopossible, and the mask layer does not need to be formed over the entiresurface of the substrate.

As shown in FIG. 15A, in a connection region 205, a wiring layer formedof the same material and through the same step as those of a secondelectrode layer is electrically connected to a wiring layer formed ofthe same material and through the same step as those of the gateelectrode layer.

A light-emitting layer 188 is formed over the first electrode layer 185.Although only one pixel is shown in FIG. 15B, electroluminescent layerscorresponding to R (red), G (green) and B (blue) are formed in thisembodiment mode.

Then, a second electrode layer 189 formed of a conductive film isprovided over the light-emitting layer 188. As the second electrodelayer 189, Al, Ag, Li, Ca, or an alloy or a compound thereof such asMgAg, MgIn, AlLi, or CaF₂, or calcium nitride may be used. In thismanner, a light-emitting element 190 including the first electrode layer185, the light-emitting layer 188, and the second electrode layer 189 isformed (refer to FIG. 15B).

In the display device of this embodiment mode shown in FIGS. 15A and15B, light from the light-emitting element 190 is emitted from the firstelectrode layer 185 side to be transmitted in a direction indicated byan arrow in FIG. 15B.

In this embodiment mode, an insulating layer may be provided as apassivation film (protective film) over the second electrode layer 189.It is effective to provide a passivation film so as to cover the secondelectrode layer 189 as described above. The passivation film may beformed using an insulating film containing silicon nitride, siliconoxide, silicon oxynitride, silicon nitride oxide, aluminum nitride,aluminum oxynitride, aluminum nitride oxide containing more nitrogenthan oxygen, aluminum oxide, diamond-like carbon (DLC), ornitrogen-containing carbon, and a single layer or a stacked layer of theinsulating films can be used. Alternatively, a siloxane resin may alsobe used.

At this time, it is preferable to form the passivation film using a filmby which favorable coverage is provided, and it is effective to use acarbon film, particularly, a DLC film for the passivation film. A DLCfilm can be formed in the temperature range from room temperature toless than or equal to 100° C.; therefore, it can also be formed easilyover the light-emitting layer 188 with low heat resistance. A DLC filmcan be formed by a plasma CVD method (typically, an RF plasma CVDmethod, a microwave CVD method, an electron cyclotron resonance (ECR)CVD method, a heat filament CVD method, or the like), a combustionmethod, a sputtering method, an ion beam evaporation method, a laserevaporation method, or the like. As a reaction gas for deposition, ahydrogen gas and a hydrocarbon-based gas (for example, CH₄, C₂H₂, C₆H₆,and the like) are used to be ionized by glow discharge, and the ions areaccelerated to impact against a cathode to which negative self-biasvoltage is applied. Further, a CN film may be formed with the use of aC₂H₄ gas and a N₂ gas as a reaction gas. A DLC film has high blockingeffect against oxygen; therefore, oxidization of the light-emittinglayer 188 can be suppressed. Accordingly, a problem such as oxidation ofthe light-emitting layer 188 during a sealing step which is performedlater can be prevented.

The substrate 150 over which the light-emitting element 190 is formedand a sealing substrate 195 are firmly attached to each other with asealing material 192, whereby the light-emitting element is sealed(refer to FIGS. 15A and 15B). As the sealing material 192, typically, avisible light curable resin, an ultraviolet light curable resin, or athermosetting resin is preferably used. For example, a bisphenol-Aliquid resin, a bisphenol-A solid resin, a bromine-containing epoxyresin, a bisphenol-F resin, a bisphenol-AD resin, a phenol resin, acresol resin, a novolac resin, a cycloaliphatic epoxy resin, an Epi-Bistype epoxy resin, a glycidyl ester resin, a glycidyl amine-based resin,a heterocyclic epoxy resin, a modified epoxy resin, or the like can beused. It is to be noted that a region surrounded by the sealing materialmay be filled with a filler 193, and nitrogen or the like may be filledand sealed by sealing in a nitrogen atmosphere. Since a bottom emissiontype is employed in this embodiment mode, the filler 193 does not needto transmit light. However, in a case where light is extracted throughthe filler 193, the filler needs to transmit light. Typically, a visiblelight curable epoxy resin, an ultraviolet light curable epoxy resin, ora thermosetting epoxy resin may be used. Through the aforementionedsteps, a display device having a display function using thelight-emitting element of this embodiment mode is completed. Further,the filler may be dripped in a liquid state to fill the display device.Through the use of a hygroscopic substance like a drying agent as thefiller, further moisture absorbing effect can be obtained, whereby theelement can be prevented from deteriorating.

A drying agent is provided in an EL display panel to preventdeterioration due to moisture in the element. In this embodiment mode,the drying agent is provided in a concave portion that is formed so asto surround the pixel region on the sealing substrate, whereby a thindesign is not hindered. Further, when the drying agent is also formed ina region corresponding to a gate wiring layer so that a moistureabsorbing area becomes wide, moisture can be effectively absorbed. Inaddition, when the drying agent is formed over a gate wiring layer whichdoes not emit light from itself, light extraction efficiency is notdecreased, either.

The light-emitting element is sealed by a glass substrate in thisembodiment mode. It is to be noted that sealing treatment is treatmentfor protecting a light-emitting element from moisture, and any of amethod for mechanically sealing the light-emitting element by a covermaterial, a method for sealing the light-emitting element with athermosetting resin or an ultraviolet light curable resin, and a methodfor sealing the light-emitting element by a thin film having a highbarrier property such as a metal oxide film or a metal nitride film isused. As the cover material, glass, ceramics, plastics, or metal can beused, and a material which transmits light is necessary to be used inthe case where light is emitted to the cover material side. The covermaterial and the substrate over which the light-emitting element isformed are attached to each other with a sealing material such as athermosetting resin or an ultraviolet light curable resin, and a sealedspace is formed through curing of the resin by heat treatment orultraviolet light irradiation treatment. It is also effective to providea moisture absorbing material typified by barium oxide in this sealedspace. This moisture absorbing material may be provided on and incontact with the sealing material, or over or in the periphery of thepartition wall so as not to shield light from the light-emittingelement. Further, the space between the cover material and the substrateover which the light-emitting element is formed can be filled with athermosetting resin or an ultraviolet light curable resin. In this case,it is effective to add a moisture absorbing material typified by bariumoxide in the thermosetting resin or the ultraviolet light curable resin.

In addition, the source electrode layer or drain electrode layer and thefirst electrode layer do not need to be directly in contact with eachother to be electrically connected, but may be connected to each otherthrough a wiring layer.

In this embodiment mode, the terminal electrode layer 178 is connectedto an FPC 194 through an anisotropic conductive layer 196 in theexternal terminal connection region 202, and electrically connected toan external portion. In addition, as shown in FIG. 15A that is a topview of the display device, the display device manufactured in thisembodiment mode includes a peripheral driver circuit region 207 and aperipheral driver circuit region 208 each including a scanning linedriver circuit in addition to the peripheral driver circuit region 204and the peripheral driver circuit region 209 each including a signalline driver circuit.

The circuit as described above is used in this embodiment mode; however,the present. invention is not limited thereto. An IC chip may be mountedby the aforementioned COG method or TAB method as the peripheral drivercircuit. Further, single or plural gate line driver circuits and sourceline driver circuits may be provided.

In the display device of the present invention, a driving method forimage display is not particularly limited, and for example, a dotsequential driving method, a line sequential driving method, an areasequential driving method, or the like may be used. Typically, a linesequential driving method may be used, and a time division gray scaledriving method and an area gray scale driving method may beappropriately used. Further, a video signal input to the source line ofthe display device may be an analog signal or a digital signal. Thedriver circuit and the like may be appropriately designed in accordancewith the video signal.

This embodiment mode can be appropriately combined with Embodiment Mode1 or 2.

In accordance with the present invention, a component such as a wiringincluded in a display device can be formed into a desired shape. Inaddition, since complicated photolithography steps can be reduced and adisplay device can be manufactured through a simplified process, loss ofmaterials and the cost can be reduced. Therefore, a high performance andhighly reliable display device can be manufactured with a high yield.

Embodiment Mode 5

A thin film transistor can be formed by employing the present invention,and a display device can be formed by using the thin film transistor.When a light-emitting element is used and a transistor for driving thelight-emitting element is to be an n-channel transistor, light isemitted from the light-emitting element in the following manner:bottom-emission, top-emission, or dual-emission. Here, a stacked layerstructure of the light-emitting element in each case will be describedwith reference to FIGS. 17A to 17C.

In this embodiment mode, channel protective thin film transistors 461,471, and 481 to which the present invention is applied are used. Thethin film transistor 481 is provided over a light-transmitting substrate480 and includes a gate electrode layer 493, a gate insulating film 497,a semiconductor layer 494, an n-type semiconductor layer 495 a, ann-type semiconductor layer 495 b, a source electrode layer or drainelectrode layer 487 a, a source electrode layer or drain electrode layer487 b, and a channel protective layer 496.

In this embodiment mode, the gate electrode layer, the semiconductorlayer, the source electrode layer, the drain electrode layer, a wiringlayer, a first electrode layer, and the like included in the displaydevice may be formed by discharging a liquid composition containing amaterial for forming the above components in a plurality of steps asshown in Embodiment Mode 1. As shown in Embodiment Mode 1, a firstconductive layer having a frame-shape is formed along the contour of thepattern of the conductive layer by a first discharging step, and asecond conductive layer is formed so as to fill inside the frame formedof the first conductive layer by a second discharging step.

Therefore, when the first conductive layer (insulating layer) whichdetermines the contour of a formation region of the conductive layer(insulating layer) is formed by applying a composition with relativelyhigh viscosity and low wettability with respect to the formation region,a side edge portion which becomes a contour of a desired pattern can beformed with high controllability. When a liquid composition with lowviscosity and high wettability with respect to the formation region isapplied inside a frame formed of the first conductive layer (insulatinglayer), space, unevenness, and the like due to bubbles and the like inor on the surface of the conductive layer are reduced, and a conductivelayer (insulating layer) which is very flat and uniform can be formed.Therefore, by separate formation of an outer-side conductive layer(insulating layer) and an inner-side conductive layer (insulatinglayer), a conductive layer (insulating layer) that has a high level ofplanarity, less defects, and a desired pattern can be formed with highcontrollability. Therefore, the process can be simplified, and loss ofmaterials and the cost can be reduced.

In this embodiment mode, an amorphous semiconductor layer is used as thesemiconductor layer. However, the present invention is not limited tothis embodiment mode, and a crystalline semiconductor layer can be usedas the semiconductor layer, and an n-type semiconductor layer can beused as the semiconductor layer having one conductivity type. Instead offormation of the n-type semiconductor layer, conductivity may beimparted to the semiconductor layer by plasma treatment with a PH₃ gas.When a crystalline semiconductor layer like polysilicon is used, thesemiconductor layer having one conductivity type is not formed, and animpurity region having one conductivity type may be formed byintroduction (addition) of an impurity to the crystalline semiconductorlayer. In addition, an organic semiconductor such as pentacene can alsobe used. When the organic semiconductor is selectively formed by adroplet discharging method or the like, the process can be simplified.

A case where a crystalline semiconductor layer is used as thesemiconductor layer will be described. First, an amorphous semiconductorlayer is crystallized to form a crystalline semiconductor layer. In acrystallization step in which an amorphous semiconductor layer iscrystallized to form a crystalline semiconductor layer, an element whichpromotes crystallization (also referred to as a catalytic element or ametal element) is added to the amorphous semiconductor layer, andcrystallization is performed by heat treatment (at 550 to 750° C. for 3minutes to 24 hours). As a metal element which promotes crystallizationof silicon, one or a plurality of kinds of metal such as iron (Fe),nickel (Ni), cobalt (Co), ruthenium (Ru), rhodium (Rh), palladium (Pd),osmium (Os), iridium (Ir), platinum (Pt), copper (Cu), and gold (Au) canbe used.

In order to remove or reduce the element which promotes crystallizationfrom the crystalline semiconductor layer, a semiconductor layercontaining an impurity element is formed to be in contact with thecrystalline semiconductor layer and is made to function as a getteringsink. As the impurity element, an impurity element imparting n-typeconductivity, an impurity element imparting p-type conductivity, a raregas element, or the like can be used. For example, one or a plurality ofkinds of elements such as phosphorus (P), nitrogen (N), arsenic (As),antimony (Sb), bismuth (Bi), boron (B), helium (He), neon (Ne), argon(Ar), krypton (Kr), and xenon (Xe) can be used. An n-type semiconductorlayer is formed to be in contact with the crystalline semiconductorlayer containing the element which promotes crystallization, and heattreatment (at temperatures of 550 to 750° C. for 3 minutes to 24 hours)is performed. The element which promotes crystallization contained inthe crystalline semiconductor layer moves into the n-type semiconductorlayer, and the element which promotes crystallization contained in thecrystalline semiconductor layer is removed or reduced, whereby thesemiconductor layer is formed. Alternatively, this n-type semiconductorlayer becomes an n-type semiconductor layer containing a metal elementwhich promotes crystallization, which is later formed into a desiredshape to be an n-type semiconductor layer. In this manner, the n-typesemiconductor layer functions as a gettering sink of the semiconductorlayer, and also as a source region or a drain region.

The crystallization step and the gettering step of the semiconductorlayer are performed by a plurality of heat treatment. In addition, thecrystallization step and the gettering step can also be performed by oneheat treatment. In this case, heat treatment may be performed afterformation of an amorphous semiconductor layer, addition of an elementwhich promotes crystallization, and formation of a semiconductor layerwhich functions as a gettering sink.

In this embodiment mode, the gate insulating layer is formed by stackinga plurality of layers, and a silicon nitride oxide film and a siliconoxynitride film are stacked on the gate electrode layer 493 side, as thegate insulating film 497 having a two-layer structure. The stackedinsulating layers are preferably formed by successive formation of thelayers at the same temperature in the same chamber while changingreaction gases with a vacuum state maintained. When the films aresuccessively formed while maintaining the vacuum state, interfacebetween the stacked films can be prevented from being contaminated.

The channel protective layer 496 may be formed by a droplet dischargingmethod using polyimide, polyvinyl alcohol, or the like. As a result, alight exposure step can be omitted. The channel protective layer can beformed using one or a plurality of kinds of an inorganic material (suchas silicon oxide, silicon nitride, silicon oxynitride, or siliconnitride oxide), a photosensitive or non-photosensitive organic material(such as an organic resin material, e.g. polyimide, acrylic, polyamide,polyimide amide, resist, or benzocyclobutene), a low-dielectric constantmaterial, and the like, or a stacked layer structure thereof. Inaddition, a siloxane material may also be used. As a manufacturingmethod, a vapor deposition method such as a plasma CVD method or athermal CVD method, or a sputtering method can be used. A dropletdischarging method, a dispenser method, or a printing method (a methodfor forming a pattern, such as screen printing or offset printing) canalso be used. An SOG film obtained by a coating method or the like canalso be used.

First, a case where light is emitted from the substrate 480 side, thatis, a case of bottom emission will be described with reference to FIG.17A. In this case, a first electrode layer 484 is in contact with thesource electrode layer or drain electrode layer 487 b. The firstelectrode layer 484, an electroluminescent layer 485, and a secondelectrode layer 486 are stacked sequentially so as to be electricallyconnected to the thin film transistor 481. The substrate 480 throughwhich light is transmitted is necessary to have at least alight-transmitting property of visible light.

A case where light is emitted to the side opposite to a substrate 460,that is, a case of top-emission will be described with reference to FIG.17B. The thin film transistor 461 can be formed similarly to the abovethin film transistor. A source electrode layer or drain electrode layer462 that is electrically connected to the thin film transistor 461 is incontact with a first electrode layer 463 to be electrically connected.The first electrode layer 463, an electroluminescent layer 464, and asecond electrode layer 465 are sequentially stacked. The sourceelectrode layer or drain electrode layer 462 is a metal layer havingreflectivity, and reflects light which is emitted from thelight-emitting element, upward as denoted by an arrow. The sourceelectrode layer or drain electrode layer 462, and the first electrodelayer 463 are stacked, and therefore, even when the first electrodelayer 463 is formed of a material having a light-transmitting propertyand transmits light, the light is reflected on the source electrodelayer or drain electrode layer 462 and then is emitted in the directionopposite to the substrate 460. Of course, the first electrode layer 463may also be formed using a metal film having reflectivity. Since lightfrom the light-emitting element is emitted through the second electrodelayer 465, the second electrode layer 465 is formed using a materialhaving at least a light-transmitting property of visible light.

A case where light is emitted to the substrate 470 side and to the sideopposite to the substrate 470 side, that is, a case of dual-emissionwill be described with reference to FIG. 17C. The thin film transistor471 is also a channel protective thin film transistor. A sourceelectrode layer or drain electrode layer 475 that is electricallyconnected to a semiconductor layer of the thin film transistor 471 iselectrically connected to a first electrode layer 472. The firstelectrode layer 472, an electroluminescent layer 473, and a secondelectrode layer 474 are sequentially stacked. At this time, if the firstelectrode layer 472 and the second electrode layer 474 are both formedusing a material having at least a light-transmitting property ofvisible light or are both formed to have thicknesses that can transmitlight, dual-emission is realized. In this case, the insulating layer andthe substrate 470 through which light is transmitted are also need tohave at least a light-transmitting property of visible light.

This embodiment mode can be appropriately combined with Embodiment Modes1 to 4.

In accordance with the present invention, a component such as a wiringincluded in a display device can be formed into a desired shape. Inaddition, since complicated photolithography steps can be reduced and adisplay device can be manufactured through a simplified process, loss ofmaterials and the cost can be reduced. Therefore, a high performance andhighly reliable display device can be manufactured with a high yield.

Embodiment Mode 6

In this embodiment mode, an example of a highly reliable display devicewhich is manufactured through a simplified process at low cost will bedescribed. More specifically, a light-emitting display device using alight-emitting element as a display element will be described.

In this embodiment mode, a structure of a light-emitting element whichcan be applied as a display element of a display device of the presentinvention will be described with reference to FIGS. 22A to 22D.

FIGS. 22A to 22D each show an element structure of a light-emittingelement, which is a light-emitting element where an electroluminescentlayer 860 formed by mixing an organic compound and an inorganic compoundis interposed between a first electrode layer 870 and a second electrodelayer 850. As shown in the drawings, the electroluminescent layer 860includes a first layer 804, a second layer 803, and a third layer 802,and there is a great feature especially in the first layer 804 and thethird layer 802.

First, the first layer 804 is a layer which has a function oftransporting holes to the second layer 803, and includes at least afirst organic compound and a first inorganic compound showing anelectron-accepting property to the first organic compound. It isimportant that the first organic compound and the first inorganiccompound are not only simply mixed but also the first inorganic compoundhas an electron-accepting property with respect to the first organiccompound. This structure generates many hole-carriers in the firstorganic compound which has originally almost no inherent carriers, and ahole-injecting and a hole-transporting property which are highlyexcellent can be obtained.

Therefore, as for the first layer 804, not only advantageous effect thatis considered to be obtained by mixing an inorganic compound (such asimprovement in heat resistance) but also excellent conductivity (inparticular, a hole-injecting property and a hole-transporting propertyin the first layer 804) can also be obtained. This excellentconductivity is advantageous effect, which cannot be obtained in aconventional hole-transporting layer in which an organic compound and aninorganic compound that do not electronically interact with each otherare simply mixed. This advantageous effect can make a drive voltagelower than conventionally. In addition, since the first layer 804 can bemade thick without causing increase in a drive voltage, a short circuitof the element due to dusts or the like can be suppressed.

It is preferable to use a hole-transporting organic compound as thefirst organic compound because hole-carriers are generated in the firstorganic compound as described above. Examples of the hole-transportingorganic compound include phthalocyanine (abbreviation: H₂Pc), copperphthalocyanine (abbreviation: CuPc), vanadyl phthalocyanine(abbreviation: VOPc), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine(abbreviation: TDATA),4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine(abbreviation: MTDATA), 1,3,5-tris[N,N-di(m-tolyl)amino]benzene(abbreviation: m-MTDAB),N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine(abbreviation: TPD), 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl(abbreviation: NPB),4,4′-bis{N-[4-di(m-tolyl)amino]phenyl-N-phenylamino}biphenyl(abbreviation: DNTPD), 4,4′,4″-tris(N-carbazolyl)triphenylamine(abbreviation: TCTA), and the like. However, the present invention isnot limited to these examples. In addition, among the compoundsdescribed above, aromatic amine compounds typified by TDATA, MTDATA,m-MTDAB, TPD, NPB, DNTPD, and TCTA can easily generate hole-carriers,and are suitable compound groups for the first organic compound.

On the other hand, the first inorganic compound may be any material aslong as the material can easily accept electrons from the first organiccompound, and various kinds of metal oxides and metal nitrides can beused. Any of transition metal oxides that belong to Groups 4 to 12 ofthe periodic table is preferable because an electron-accepting propertyis easily provided. Specifically, titanium oxide, zirconium oxide,vanadium oxide, molybdenum oxide, tungsten oxide, rhenium oxide,ruthenium oxide, zinc oxide, and the like can be given. In addition,among the metal oxides described above, any of transition metal oxidesthat belong to Groups 4 to 8 of the periodic table mostly has a highelectron-accepting property, which is a preferable group. In particular,vanadium oxide, molybdenum oxide, tungsten oxide, and rhenium oxide arepreferable because they can be formed by vacuum evaporation and can beeasily used.

It is to be noted that the first layer 804 may be formed by stacking aplurality of layers each including a combination of the organic compoundand the inorganic compound as described above, or may further includeanother organic compound or inorganic compound.

Next, the third layer 802 will be described. The third layer 802 is alayer which has a function of transporting electrons to the second layer803, and includes at least a third organic compound and a thirdinorganic compound showing an electron-donating property to the thirdorganic compound. It is important that the third organic compound andthe third inorganic compound are not only simply mixed but also thethird inorganic compound has an electron-denoting property with respectto the third organic compound. This structure generates manyelectron-carriers in the third organic compound which has originallyalmost no inherent carriers, and an electron-injecting and anelectron-transporting property which are highly excellent can beobtained.

Therefore, as for the third layer 802, not only advantageous effect thatis considered to be obtained by mixing an inorganic compound (such asimprovement in heat resistance) but also excellent conductivity (inparticular, an electron-injecting property and an electron-transportingproperty in the third layer 802) can also be obtained. This excellentconductivity is advantageous effect, which cannot be obtained in aconventional electron-transporting layer in which an organic compoundand an inorganic compound that do not electronically interact with eachother are simply mixed. This advantageous effect can make a drivevoltage lower than conventionally. In addition, since the third layer802 can be made thick without causing increase in a drive voltage, ashort circuit of the element due to dusts or the like can be suppressed.

It is preferable to use an electron-transporting organic compound as thethird organic compound because electron-carriers are generated in thethird organic compound as described above. Examples of theelectron-transporting organic compound includetris(8-quinolinolato)aluminum (abbreviation: Alq₃),tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq₃),bis(10-hydroxybenzo[h]-quinolinato)beryllium (abbreviation: BeBq₂),bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum (abbreviation:BAlq), bis[2-(2′-hydroxyphenyl)benzoxazolato]zinc (abbreviation:Zn(BOX)₂), bis[2-(2′-hydroxyphenyl)benzothiazolato]zinc (abbreviation:Zn(BTZ)₂), bathophenanthroline (abbreviation: BPhen), bathocuproin(abbreviation: BCP),2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),2,2′,2″-(1,3,5-benzenetriyl)-tris(1-phenyl-1H-benzimidazole)(abbreviation: TPBI),3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole(abbreviation: TAZ),3-(4-biphenylyl)-4-(4-ethylphenyl)-5-(4-tert-butylphenyl)-1,2,4-triazole(abbreviation: p-EtTAZ), and the like. However, the present invention isnot limited to these examples. In addition, among the compoundsmentioned above, chelate metal complexes having a chelate ligandincluding an aromatic ring typified by Alq₃, Almq₃, BeBq₂, BAlq,Zn(BOX)₂, and Zn(BTZ)₂, organic compounds having a phenanthrolineskeleton typified by BPhen and BCP, and organic compounds having anoxadiazole skeleton typified by PBD and OXD-7 can easily generateelectron-carriers, and are suitable compound groups for the thirdorganic compound.

On the other hand, the third inorganic compound may be any material aslong as the material can easily donate electrons to the third organiccompound, and various kinds of metal oxide and metal nitride can beused. Alkali metal oxide, alkaline-earth metal oxide, rare-earth metaloxide, alkali metal nitride, alkaline-earth metal nitride, andrare-earth metal nitride are preferable because an electron-donatingproperty is easily provided. Specifically, for example, lithium oxide,strontium oxide, barium oxide, erbium oxide, lithium nitride, magnesiumnitride, calcium nitride, yttrium nitride, lanthanum nitride, and thelike can be given. In particular, lithium oxide, barium oxide, lithiumnitride, magnesium nitride, and calcium nitride are preferable becausethey can be formed by vacuum evaporation and can be easily used.

It is to be noted that the third layer 802 may be formed by stacking aplurality of layers each including a combination of the organic compoundand the inorganic compound as described above, or may further includeanother organic compound or inorganic compound.

Then, the second layer 803 will be described. The second layer 803 is alayer which has a function of emitting light, and includes a secondorganic compound that has a light-emitting property. A second inorganiccompound may also be included. The second layer 803 can be formed usingvarious light-emitting organic compounds and inorganic compounds.However, since it is believed to be hard to flow a current through thesecond layer 803 compared to the first layer 804 or the third layer 802,the thickness of the second layer 803 is preferably approximately 10 to100 nm.

There are no particular limitations on the second organic compound aslong as it is a light-emitting organic compound. Examples of the secondorganic compound include, for example, 9,10-di(2-naphthyl)anthracene(abbreviation: DNA), 9,10-di(2-naphthyl)-2-tert-butylanthracene(abbreviation: t-BuDNA), 4,4′-bis(2,2-diphenylvinyl)biphenyl(abbreviation: DPVBi), coumarin 30, coumarin 6, coumarin 545, coumarin545T, perylene, rubrene, periflanthene,2,5,8,11-tetra(tert-butyl)perylene (abbreviation: TBP),9,10-diphenylanthracene (abbreviation: DPA), 5,12-diphenyltetracene,4-(dicyanomethylene)-2-methyl-[p-(dimethylamino)styryl]-4H-pyran(abbreviation: DCM1),4-(dicyanomethylene)-2-methyl-6-[2-oulolidin-9-yl)ethenyl]-4H-pyran(abbreviation: DCM2),4-(dicyanomethylene)-2,6-bis[p-(dimethylamino)styryl]-4H-pyran(abbreviation: BisDCM), and the like. In addition, it is also possibleto use a compound capable of emitting phosphorescence such asbis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(picolinate)(abbreviation: FIrpic),bis{2-[3′,5′-bis(trifluoromethyl)phenyl]pyridinato-N,C^(2′)}iridium(picolinate)(abbreviation: Ir(CF₃ppy)₂(pic)),tris(2-phenylpyridinato-N,C^(2′))iridium (abbreviation: Ir(ppy)₃),bis(2-phenylpyridinato-N,C^(2′))iridium(acetylacetonate) (abbreviation:Ir(ppy)₂(acac)),bis[2-(2′-thienyl)pyridinato-N,C^(3′)]iridium(acetylacetonate)(abbreviation: Ir(thp)₂(acac)),bis(2-phenylquinolinato-N,C^(2′))iridium(acetylacetonate) (abbreviation:Ir(pq)₂(acac)), orbis[2-(2′-benzothienyl)pyridinato-N,C^(3′)]iridium(acetylacetonate)(abbreviation: Ir(btp)₂(acac)).

Further, a triplet excitation light-emitting material containing a metalcomplex or the like may be used for the second layer 803 in addition toa singlet excitation light-emitting material. For example, among pixelsemitting light of red, green, and blue, a pixel emitting light of redwhose luminance is reduced by half in a relatively short time is formedby using a triplet excitation light-emitting material and the otherpixels are formed by using a singlet excitation light-emitting material.A triplet excitation light-emitting material has a feature of favorablelight-emitting efficiency and less power consumption to obtain the sameluminance. In other words, when a triplet excitation light-emittingmaterial is used for a red pixel, only a small amount of current needsto be applied to a light-emitting element; thus, reliability can beimproved. A pixel emitting light of red and a pixel emitting light ofgreen may be formed by using a triplet excitation light-emittingmaterial and a pixel emitting light of blue may be formed by using asinglet excitation light-emitting material to achieve low powerconsumption as well. Low power consumption can be further achieved byformation of a light-emitting element emitting light of green that hashigh visibility for human eyes with the use of a triplet excitationlight-emitting material.

The second layer 803 may include not only the second organic compound asdescribed above, which produces light-emission, but also another organiccompound which is added thereto. Examples of organic compounds that canbe added include TDATA, MTDATA, m-MTDAB, TPD, NPB, DNTPD, TCTA, Alq₃,Almq₃, BeBq₂, BAlq, Zn(BOX)₂, Zn(BTZ)₂, BPhen, BCP, PBD, OXD-7, TPBI,TAZ, p-EtTAZ, DNA, t-BuDNA, and DPVBi, which are mentioned above, andfurther, 4,4′-bis(N-carbazolyl)biphenyl (abbreviation: CBP),1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB), and thelike. However, the present invention is not limited to these examples.It is preferable that the organic compound, which is added in additionto the second organic compound, have larger excitation energy than thatof the second organic compound and be added by the larger amount thanthe second organic compound in order to make the second organic compoundemit light efficiently (which makes it possible to prevent concentrationquenching of the second organic compound). Alternatively, as anotherfunction, the added organic compound may emit light along with thesecond organic compound (which makes it possible to emit white light orthe like).

The second layer 803 may have a structure to perform color display byproviding each pixel with a light-emitting layer having a differentemission wavelength range. Typically, a light-emitting layercorresponding to each color of R (red), G (green), and B (blue) isformed. Also in this case, color purity can be improved and a pixelportion can be prevented from having a mirror surface (reflection) byproviding the light-emission side of the pixel with a filter whichtransmits light of an emission wavelength range of the light. Byprovision of a filter, a circularly polarizing plate or the like thathas been conventionally considered to be necessary can be omitted, andfurther, the loss of light emitted from the light-emitting layer can beeliminated. Further, change in a color tone, which occurs when a pixelportion (display screen) is obliquely seen, can be reduced.

Either a low-molecular organic light-emitting material or ahigh-molecular organic light-emitting material may be used for amaterial of the second layer 803. A high-molecular organiclight-emitting material is physically stronger compared to alow-molecular material and is superior in durability of the element. Inaddition, a high-molecular organic light-emitting material can be formedby coating; therefore, the element can be relatively easilymanufactured.

The emission color is determined depending on a material forming thelight-emitting layer; therefore, a light-emitting element which exhibitsdesired light-emission can be formed by selecting an appropriatematerial for the light-emitting layer. As a high-molecularelectroluminescent material which can be used for forming alight-emitting layer, a polyparaphenylene-vinylene-based material, apolyparaphenylene-based material, a polythiophene-based material, or apolyfluorene-based material, and the like can be used.

As the polyparaphenylene-vinylene-based material, a derivative ofpoly(paraphenylenevinylene) [PPV] such aspoly(2,5-dialkoxy-1,4-phenylenevinylene) [RO-PPV],poly(2-(2′-ethyl-hexoxy)-5-methoxy-1,4-phenylenevinylene) [MEH-PPV], orpoly(2-(dialkoxyphenyl)-1,4-phenylenevinylene) [ROPh-PPV] can be given.As the polyparaphenylene-based material, a derivative ofpolyparaphenylene [PPP] such as poly(2,5-dialkoxy-1,4-phenylene)[RO-PPP] or poly(2,5-dihexoxy-1,4-phenylene) can be given. As thepolythiophene-based material, a derivative of polythiophene [PT] such aspoly(3-alkylthiophene) [PAT], poly(3-hexylthiophen) [PHT],poly(3-cyclohexylthiophen) [PCHT], poly(3-cyclohexyl-4-methylthiophene)[PCHMT], poly(3,4-dicyclohexylthiophene) [PDCHT],poly[3-(4-octylphenyl)-thiophene] [POPT], orpoly[3-(4-octylphenyl)-2,2bithiophene] [PTOPT] can be given. As thepolyfluorene-based material, a derivative of polyfluorene [PF] such aspoly(9,9-dialkylfluorene) [PDAF] or poly(9,9-dioctylfluorene) [PDOF] canbe given.

The second inorganic compound may be any inorganic compound as long aslight-emission of the second organic compound is not easily quenched bythe inorganic compound, and various kinds of metal oxide and metalnitride can be used. In particular, a metal oxide having a metal thatbelongs to Group 13 or 14 of the periodic table is preferable becauselight-emission of the second organic compound is not easily quenched,and specifically, aluminum oxide, gallium oxide, silicon oxide, andgermanium oxide are preferable. However, the second inorganic compoundis not limited thereto.

It is to be noted that the second layer 803 may be formed by stacking aplurality of layers each including a combination of the organic compoundand the inorganic compound as described above, or may further includeanother organic compound or inorganic compound. A layer structure of thelight-emitting layer can be changed, and an electrode layer forinjecting electrons may be provided or a light-emitting material may bedispersed, instead of providing no specific electron-injecting region orlight-emitting region. Such a change can be permitted unless it departsfrom the spirit of the present invention.

A light-emitting element formed by using the above materials emits lightby being forwardly biased. A pixel of a display device which is formedby using a light-emitting element can be driven by a simple matrix(passive matrix) mode or an active matrix mode. In any case, each pixelemits light by application of a forward bias voltage thereto at aspecific timing; however, the pixel is in a non-emitting state for acertain period. Reliability of a light-emitting element can be improvedby application of a reverse bias voltage in the non-emitting time. In alight-emitting element, there is a deterioration mode in which emissionintensity is decreased under constant driving conditions or adeterioration mode in which a non-light-emitting region is enlarged inthe pixel and luminance is apparently decreased. However, progression ofdeterioration can be slowed down by alternating current driving where abias voltage is applied forwardly and reversely; thus, reliability of alight-emitting display device can be improved. In addition, eitherdigital driving or analog driving can be applied.

A color filter (colored layer) may be formed over a sealing substrate.The color filter (colored layer) can be formed by an evaporation methodor a droplet discharging method. High-resolution display can beperformed with the use of the color filter (colored layer). This isbecause a broad peak can be modified to be sharp in an emission spectrumof each of R, G, and B by the color filter (colored layer).

Full color display can be performed by the steps of forming a materialemitting light of a single color and combining with a color filter or acolor conversion layer. Preferably, the color filter (colored layer) orthe color conversion layer is formed over, for example, a sealingsubstrate and attached to an element substrate.

Of course, display of a single color emission may also be performed. Forexample, an area color type display device may be manufactured by usingsingle color emission. The area color type is suitable for a passivematrix display portion, and can mainly display characters and symbols.

Materials for the first electrode layer 870 and the second electrodelayer 850 are necessary to be selected considering the work function.The first electrode layer 870 and the second electrode layer 850 can beeither an anode or a cathode depending on the pixel structure. In a casewhere the polarity of a driving thin film transistor is a p-channeltype, the first electrode layer 870 preferably serves as an anode andthe second electrode layer 850 preferably serves as a cathode as shownin FIG. 22A. In a case where the polarity of the driving thin filmtransistor is an n-channel type, the first electrode layer 870preferably serves as a cathode and the second electrode layer 850preferably serves as an anode as shown in FIG. 22B. Materials that canbe used for the first electrode layer 870 and the second electrode layer850 will be described. It is preferable to use a material having a highwork function (specifically, a material having a work function of 4.5 eVor more) for one of the first electrode layer 870 and the secondelectrode layer 850, which serves as an anode, and a material having alow work function (specifically, a material having a work function of3.5 eV or less) for the other electrode layer which serves as a cathode.However, since the first layer 804 is superior in a hole-injectingproperty and a hole-transporting property and the third layer 802 issuperior in an electron-injecting property and an electron transportingproperty, both the first electrode layer 870 and the second electrodelayer 850 are scarcely restricted by a work function, and variousmaterials can be used.

The light-emitting elements shown in FIGS. 22A and 22B have a structurewhere light is extracted from the first electrode layer 870; thus, thesecond electrode layer 850 does not need to have a light-transmittingproperty. The second electrode layer 850 may be formed from a filmmainly containing an element of Ti, Ni, W, Cr, Pt, Zn, Sn, In, Ta, Al,Cu, Au, Ag, Mg, Ca, Li and Mo, or an alloy material or a compoundmaterial containing the element as its main component such as TiN,TiSi_(X)N_(Y), WSi_(X), WN_(X), WSi_(X)N_(Y), or NbN; or a stacked filmthereof with a total film thickness of 100 to 800 nm.

The second electrode layer 850 can be formed by an evaporation method, asputtering method, a CVD method, a printing method, a dispenser method,a droplet discharging method, or the like.

In addition, when the second electrode layer 850 is formed using alight-transmitting conductive material similarly to the material usedfor the first electrode layer 870, light can also be extracted from thesecond electrode layer 850, and a dual emission structure can beobtained, in which light emitted from the light-emitting element isemitted from both the first electrode layer 870 and the second electrodelayer 850.

It is to be noted that the light-emitting element of the presentinvention can have variations by changing types of the first electrodelayer 870 and the second electrode layer 850.

FIG. 22B shows a case where the third layer 802, the second layer 803,and the first layer 804 are sequentially provided from the firstelectrode layer 870 side in the electroluminescent layer 860.

As described above, in the light-emitting element of the presentinvention, the layer interposed between the first electrode layer 870and the second electrode layer 850 is formed using theelectroluminescent layer 860 including a layer in which an organiccompound and an inorganic compound are combined. The light-emittingelement is an organic-inorganic composite light-emitting elementprovided with layers (that is, the first layer 804 and the third layer802) that provide functions, a high carrier-injecting property andcarrier-transporting property, by mixing an organic compound and aninorganic compound. Such functions as high carrier-injecting propertyand carrier-transporting property are not obtainable from only eitherone of the organic compound or the inorganic compound. In addition, thefirst layer 804 and the third layer 802 particularly need to be layersin which an organic compound and an inorganic compound are combined whenprovided on the first electrode layer 870 side, and may also containonly one of an organic compound and an inorganic compound when providedon the second electrode layer 850 side.

Further, various methods can be used as a method for forming theelectroluminescent layer 860, which is a layer in which an organiccompound and an inorganic compound are mixed. For example, the methodsinclude a co-evaporation method for evaporating both an organic compoundand an inorganic compound by resistance heating. Besides, forco-evaporation, an inorganic compound may be evaporated by an electronbeam (EB) while evaporating an organic compound by resistance heating.Moreover, the methods also include a method for sputtering an inorganiccompound while evaporating an organic compound by resistance heating todeposit the both at the same time. In addition, the electroluminescentlayer may also be formed by a wet method.

In the same manner, for the first electrode layer 870 and the secondelectrode layer 850, evaporation by resistance heating, EB evaporation,sputtering, a wet method, or the like can be used.

In FIG. 22C, an electrode layer having reflectivity is used for thefirst electrode layer 870, and an electrode layer having alight-transmitting property is used for the second electrode layer 850in the structure of FIG. 22A. Light emitted from the light-emittingelement is reflected on the first electrode layer 870, transmittedthrough the second electrode layer 850, and is emitted to an externalportion. In the same manner, in FIG. 22D, an electrode layer havingreflectivity is used for the first electrode layer 870, and an electrodelayer having a light-transmitting property is used for the secondelectrode layer 850 in the structure of FIG. 22B. Light emitted from thelight-emitting element is reflected on the first electrode layer 870,transmitted through the second electrode layer 850, and is emitted to anexternal portion.

This embodiment mode can be appropriately combined with other embodimentmodes describing a display device having a light-emitting element.

In accordance with the present invention, a component such as a wiringincluded in a display device can be formed into a desired shape. Inaddition, since complicated photolithography steps can be reduced and adisplay device can be manufactured through a simplified process, loss ofmaterials and the cost can be reduced. Therefore, a high performance andhighly reliable display device can be manufactured with a high yield.

This embodiment mode may be appropriately combined with Embodiment Modes1 to 5.

Embodiment Mode 7

In this embodiment mode, an example of a highly reliable display devicewhich is manufactured through a simplified process at low cost will bedescribed. More specifically, a light-emitting display device using alight-emitting element as a display element will be described. In thisembodiment mode, a structure of a light-emitting element which can beapplied as a display element of a display device of the presentinvention will be described with reference to FIGS. 23A to 23C and FIGS.24A to 24C.

A light-emitting element utilizing electroluminescence is distinguishedby whether a light-emitting material is an organic compound or aninorganic compound. In general, the former is called an organic ELelement, and the latter is called an inorganic EL element.

The inorganic EL element is classified into a dispersion type inorganicEL element and a thin-film type inorganic EL element, depending on itselement structure. The former and the latter are different in that theformer has an electroluminescent layer where particles of alight-emitting material are dispersed in a binder whereas the latter hasan electroluminescent layer formed of a thin film of a light-emittingmaterial. However, the former and the latter have in common thatelectrons accelerated by a high electric field are necessary. It is tobe noted that, as a mechanism of light-emission that is obtained, thereare donor-acceptor recombination type light-emission that utilizes adonor level and an acceptor level, and localized type light-emissionthat utilizes inner-shell electron transition of a metal ion. Ingeneral, in many cases, a dispersion type inorganic EL element hasdonor-acceptor recombination type light-emission, and a thin-film typeinorganic EL element has localized type light-emission.

The light-emitting material that can be used in the present inventionincludes a base material and an impurity element to be a light-emissioncenter. By changing an impurity element that is contained,light-emission of various colors can be obtained. As a method forforming the light-emitting material, various methods such as a solidphase method and a liquid phase method (a coprecipitation method) can beused. Further, an evaporative decomposition method, a doubledecomposition method, a method by heat decomposition reaction of aprecursor, a reversed micelle method, a method in which such a method iscombined with high-temperature baking, a liquid phase method such as alyophilization method, or the like can also be used.

A solid phase method is a method in which a base material, and animpurity element or a compound containing an impurity element areweighed, mixed in a mortar, heated in an electric furnace, and baked tobe reacted, whereby the impurity element is contained in the basematerial. The baking temperature is preferably 700 to 1500° C. This isbecause the solid reaction does not progress when the temperature is toolow, whereas the base material is decomposed when the temperature is toohigh. The baking may be performed in a powder state; however, it ispreferable to perform the baking in a pellet state. Although the bakingneeds to be performed at relatively high temperature, the solid phasemethod is easy; thus, the solid phase method has high productivity andis suitable for mass production.

A liquid phase method (coprecipitation method) is a method in which abase material or a compound containing a base material is reacted withan impurity element or a compound containing an impurity element in asolution, dried, and then baked. Particles of a light-emitting materialare distributed uniformly, and the reaction can progress even when thegrain size is small and the baking temperature is low.

As a base material used for a light-emitting material, sulfide, oxide,or nitride can be used. As sulfide, for example, zinc sulfide (ZnS),cadmium sulfide (CdS), calcium sulfide (CaS), yttrium sulfide (Y₂S₃),gallium sulfide (Ga₂S₃), strontium sulfide (SrS), barium sulfide (BaS),or the like can be used. As oxide, for example, zinc oxide (ZnO),yttrium oxide (Y₂O₃), or the like can be used. As nitride, for example,aluminum nitride (AlN), gallium nitride (GaN), indium nitride (InN), orthe like can be used. Further, zinc selenide (ZnSe), zinc telluride(ZnTe), or the like can also be used, and a ternary mixed crystal suchas calcium-gallium sulfide (CaGa₂S₄), strontium-gallium sulfide(SrGa₂S₄), or barium-gallium sulfide (BaGa₂S₄) may also be used.

As a light-emission center of localized type light-emission, manganese(Mn), copper (Cu), samarium (Sm), terbium (Th), erbium (Er), thulium(Tm), europium (Eu), cerium (Ce), praseodymium (Pr), or the like can beused. It is to be noted that a halogen element such as fluorine (F) orchlorine (Cl) may be added. A halogen element can be used as chargecompensation.

On the other hand, as a light-emission center of donor-acceptorrecombination type light-emission, a light-emitting material containinga first impurity element which forms a donor level and a second impurityelement which forms an acceptor level can be used. As the first impurityelement, for example, fluorine (F), chlorine (Cl), aluminum (Al), or thelike can be used. As the second impurity element, for example, copper(Cu), silver (Ag), or the like can be used.

In a case where the light-emitting material of donor-acceptorrecombination type light-emission is synthesized by a solid phasemethod, a base material, the first impurity element or a compoundcontaining the first impurity element, and the second impurity elementor a compound containing the second impurity element are each weighed,mixed in a mortar, heated in an electric furnace, and baked. As the basematerial, any of the above described base materials can be used. As thefirst impurity element or the compound containing the first impurityelement, for example, fluorine (F), chlorine (Cl), aluminum sulfide(Al₂S₃), or the like can be used. As the second impurity element or thecompound containing the second impurity element, for example, copper(Cu), silver (Ag), copper sulfide (Cu₂S), silver sulfide (Ag₂S), or thelike can be used. The baking temperature is preferably 700 to 1500° C.This is because the solid reaction does not progress when thetemperature is too low, whereas the base material is decomposed when thetemperature is too high. It is to be noted that although the baking maybe performed in a powder state, it is preferable to perform the bakingin a pellet state.

As the impurity element in the case of utilizing solid reaction, thecompounds containing the first impurity element and the second impurityelement may be combined. In this case, since the impurity element iseasily diffused and solid reaction progresses easily, a uniformlight-emitting material can be obtained. Further, since an unnecessaryimpurity element does not enter, a light-emitting material having highpurity can be obtained. As the compounds containing the first impurityelement and the second impurity element, for example, copper chloride(CuCl), silver chloride (AgCl), or the like can be used.

It is to be noted that the concentration of these impurity elements maybe 0.01 to 10 atomic % with respect to the base material, and ispreferably 0.05 to 5 atomic %.

In the case of a thin-film type inorganic EL element, anelectroluminescent layer is a layer containing the above light-emittingmaterial, which can be formed by a vacuum evaporation method such as aresistance heating evaporation method or an electron beam evaporation(EB evaporation) method, a physical vapor deposition (PVD) method suchas a sputtering method, a chemical vapor deposition (CVD) method such asa metal organic CVD method or a low-pressure hydride transport CVDmethod, an atomic layer epitaxy (ALE) method, or the like.

FIGS. 23A to 23C each show an example of a thin-film type inorganic ELelement that can be used as a light-emitting element. In FIGS. 23A to23C, each light-emitting element includes a first electrode layer 50, anelectroluminescent layer 52, and a second electrode layer 53

The light-emitting elements shown in FIGS. 23B and 23C each have astructure where an insulating layer is provided between the electrodelayer and the electroluminescent layer of the light-emitting element ofFIG. 23A. The light-emitting element shown in FIG. 23B has an insulatinglayer 54 between the first electrode layer 50 and the electroluminescentlayer 52. The light-emitting element shown in FIG. 23C includes aninsulating layer 54 a between the first electrode layer 50 and theelectroluminescent layer 52, and an insulating layer 54 b between thesecond electrode layer 53 and the electroluminescent layer 52. In thismanner, the insulating layer may be provided between theelectroluminescent layer and one of the electrode layers that sandwichesthe electroluminescent layer, or the insulating layer may be providedbetween the electroluminescent layer and the first electrode layer andbetween the electroluminescent layer and the second electrode layer.Moreover, the insulating layer may be a single layer or a stacked layerincluding a plurality of layers.

In addition, although the insulating layer 54 is provided so as to be incontact with the first electrode layer 50 in FIG. 23B, the insulatinglayer 54 may be provided so as to be in contact with the secondelectrode layer 53 by reversing the order of the insulating layer andthe electroluminescent layer.

In the case of a dispersion type inorganic EL element, anelectroluminescent layer film where particles of a light-emittingmaterial are dispersed in a binder is formed. When particles withdesired grain sizes cannot be obtained by a manufacturing method of alight-emitting material, a light-emitting material may be processed intoa particle state by being crushed in a mortar or the like. The binderrefers to a substance for fixing particles of a light-emitting materialin a dispersed state to keep a shape of an electroluminescent layer. Thelight-emitting material is uniformly dispersed and fixed in theelectroluminescent layer by the binder.

In the case of a dispersion type inorganic EL element, as a formationmethod of an electroluminescent layer, a droplet discharging methodwhich can selectively form an electroluminescent layer, a printingmethod (such as screen printing or offset printing), a coating methodsuch as a spin coating method, a dipping method, a dispenser method, orthe like can be used. There are no particular limitations on thethickness of the light-emitting layer; however, a thickness of 10 to1000 nm is preferable. In addition, in the electroluminescent layercontaining a light-emitting material and a binder, a ratio of thelight-emitting material is preferably set to be greater than or equal to50 wt % and less than or equal to 80 wt %.

FIGS. 24A to 24C each show an example of a dispersion type inorganic ELelement that can be used as a light-emitting element. In FIG. 24A, thelight-emitting element has a stacked layer structure of a firstelectrode layer 60, an electroluminescent layer 62, and a secondelectrode layer 63, where a light-emitting material 61 held by a binderis contained in the electroluminescent layer 62.

As the binder that can be used in this embodiment mode, an organicmaterial or an inorganic material can be used, or a mixed material of anorganic material and an inorganic material may also be used. As theorganic material, a resin such as a polymer having a relatively highdielectric constant like a cyanoethyl cellulose-based resin,polyethylene, polypropylene, a polystyrene-based resin, a siliconeresin, an epoxy resin, or vinylidene fluoride can be used. In addition,a heat-resistant high molecular material such as aromatic polyamide orpolybenzimidazole, or a siloxane resin may be used. A siloxane resincorresponds to a resin containing a Si—O—Si bond. Siloxane is composedof a skeleton structure formed by the bond of silicon (Si) and oxygen(O). As a substituent thereof, an organic group containing at leasthydrogen (such as an alkyl group or aryl group) is used. In addition, afluoro group may be used as the substituent. Further, a fluoro group andan organic group containing at least hydrogen may be used as thesubstituent. Moreover, a resin material such as a vinyl resin, e.g.polyvinyl alcohol or polyvinyl butyral, a phenol resin, a novolac resin,an acrylic resin, a melamine resin, a urethane resin, or an oxazoleresin (polybenzoxazole) may also be used. A dielectric constant can alsobe controlled by mixing these resins with high-dielectric constantmicroparticles of barium titanate (BaTiO₃), strontium titanate (SrTiO₃),or the like as appropriate.

As the inorganic material contained in the binder, a material such assilicon oxide (SiO_(x)), silicon nitride (SiN_(x)), silicon containingoxygen and nitrogen, aluminum nitride (AlN), aluminum containing oxygenand nitrogen, aluminum oxide (Al₂O₃), titanium oxide (TiO₂), BaTiO₃,SrTiO₃, lead titanate (PbTiO₃), potassium niobate (KNbO₃), lead niobate(PbNbO₃), tantalum oxide (Ta₂O₅), barium tantalate (BaTa₂O₆), lithiumtantalate (LiTaO₃), yttrium oxide (Y₂O₃), zirconium oxide (ZrO₂), andother substances containing an inorganic material can be used. By mixingthe organic material with a high-dielectric constant inorganic material(by addition or the like), a dielectric constant of anelectroluminescent layer containing a light-emitting material and abinder can be better controlled and further increased. When a mixedlayer of an inorganic material and an organic material is used for thebinder to have a high dielectric constant, larger electric charge can beinduced by the light-emitting material.

In a manufacturing process, the light-emitting material is dispersed ina solution containing a binder. As a solvent of the solution containinga binder that can be used in this embodiment mode, it is preferable toselect such a solvent that dissolves a binder material and can make asolution with the viscosity which is appropriate for a method forforming the electroluminescent layer (various wet processes) and adesired film thickness. An organic solvent or the like can be used, andfor example, when a siloxane resin is used as the binder, propyleneglycolmonomethyl ether, propylene glycolmonomethyl ether acetate (alsocalled PGMEA), 3-methoxy-3-methyl-1-butanol (also called MMB), or thelike can be used.

The light-emitting elements shown in FIGS. 24B and 24C each have astructure in which an insulating layer is provided between the electrodelayer and the electroluminescent layer of the light-emitting element ofFIG. 24A. The light-emitting element shown in FIG. 24B has an insulatinglayer 64 between a first electrode layer 60 and an electroluminescentlayer 62. The light-emitting element shown in FIG. 24C has an insulatinglayer 64 a between the first electrode layer 60 and theelectroluminescent layer 62, and an insulating layer 64 b between thesecond electrode layer 63 and the electroluminescent layer 62. In thismanner, the insulating layer may be provided between theelectroluminescent layer and one of the electrode layers that sandwichesthe electroluminescent layer, or the insulating layer may be providedbetween the electroluminescent layer and the first electrode layer andbetween the electroluminescent layer and the second electrode layer.Moreover, the insulating layer may be a single layer or a stacked layerincluding a plurality of layers.

In addition, although the insulating layer 64 is provided so as to be incontact with the first electrode layer 60 in FIG. 24B, the insulatinglayer 64 may be provided so as to be in contact with the secondelectrode layer 63 by reversing the order of the insulating layer andthe electroluminescent layer.

Although the insulating layers 54 and 64 in FIGS. 23B, 23C, 24B and 24Care not particularly limited, such insulating layers preferably havehigh dielectric strength and dense film qualities, and more preferablyhave a high dielectric constant. For example, silicon oxide (SiO₂),yttrium oxide (Y₂O₃), titanium oxide (TiO₂), aluminum oxide (Al₂O₃),hafnium oxide (HfO₂), tantalum oxide (Ta₂O₅), barium titanate (BaTiO₃),strontium titanate (SrTiO₃), lead titanate (PbTiO₃), silicon nitride(Si₃N₄), zirconium oxide (ZrO₂), or the like, or a mixed film or astaked layer film of two or more kinds thereof can be used. Theseinsulating films can be formed by sputtering, evaporation, CVD, or thelike. In addition, the insulating layers may be formed by dispersingparticles of these insulating materials in the binder. The bindermaterial may be formed with the same material and by the same method asthe binder contained in the electroluminescent layer. A thickness ofsuch an insulating layer is not particularly limited, and a filmthickness of 10 to 1000 nm is preferable.

The light-emitting element shown in this embodiment mode can emit lightwhen a voltage is applied between the pair of electrodes whichsandwiches the electroluminescent layer, and can be operated by directcurrent driving or alternating current driving.

In accordance with the present invention, a component such as a wiringincluded in a display device or the like can be formed into a desiredshape. In addition, since complicated photolithography steps can bereduced and a display device can be manufactured through a simplifiedprocess, loss of materials and the cost can be reduced. Therefore, ahigh performance and highly reliable display device can be manufacturedwith a high yield.

This embodiment mode can be appropriately combined with Embodiment Modes1 to 5.

Embodiment Mode 8

In this embodiment mode, an example of a highly reliable display devicewhich is manufactured through a simplified process at low cost will bedescribed. More specifically, a liquid crystal display device using aliquid crystal display element as a display element will be described.

FIG. 19A is a top view of a liquid crystal display device, and FIG. 19Bis a cross-sectional view taken along a line G-H of FIG. 19A. In the topview of FIG. 19A, an anti-reflective film is omitted.

As shown in FIG. 19A, a pixel region 606, a driving circuit region 608 awhich is a scanning line driving circuit, and a driving circuit region608 b which is a scanning line driving circuit are sealed between asubstrate 600 and a counter substrate 695 with a sealing material 692. Adriving circuit region 607 which is a signal line driver circuit formedwith an IC driver is provided over the substrate 600. A transistor 622and a capacitor 623 are provided in the pixel region 606. A drivercircuit having transistors 620 and 621 is provided in the drivingcircuit region 608 b. An insulating substrate can be used as thesubstrate 600 as in the above embodiment modes. Although there is aconcern that a substrate formed of a synthetic resin generally has alower temperature limit compared to another substrate, the substrateformed of a synthetic resin can be used when a manufacturing process iscarried out using a substrate with high heat resistance and then thesubstrate formed of a synthetic resin displaces the substrate with highheat resistance.

In this embodiment mode, a gate electrode layer, a semiconductor layer,a source electrode layer, a drain electrode layer, a wiring layer, afirst electrode layer, and the like included in the display device maybe formed by discharging a liquid composition containing a material forforming the above components in a plurality of steps as shown inEmbodiment Mode 1. As shown in Embodiment Mode 1, a first conductivelayer having a frame-shape is formed along the contour of the pattern ofthe conductive layer by a first discharging step, and a secondconductive layer is formed so as to fill inside the frame formed of thefirst conductive layer by a second discharging step.

Therefore, when the first conductive layer (insulating layer) whichdetermines the contour of a formation region of the conductive layer(insulating layer) is formed by applying a composition with relativelyhigh viscosity and low wettability with respect to the formation region,a side edge portion which becomes a contour of a desired pattern can beformed with high controllability. When a liquid composition with lowviscosity and high wettability with respect to the formation region isapplied inside a frame formed of the first conductive layer (insulatinglayer), space, unevenness, and the like due to bubbles and the like inor on the surface of the conductive layer are reduced, and a conductivelayer (insulating layer) which is very flat and uniform can be formed.Therefore, by separate formation of an outer-side conductive layer(insulating layer) and an inner-side conductive layer (insulatinglayer), a conductive layer (insulating layer) that has a high level ofplanarity, less defects, and a desired pattern can be formed with highcontrollability. Therefore, the process can be simplified, and loss ofmaterials and the cost can be reduced.

In the pixel region 606, the transistor 622 which is to be a switchingelement is provided over the substrate 600, with base films 604 a and604 b interposed therebetween. In this embodiment mode, a multi-gatethin film transistor (TFT) is used as the transistor 622, which includesa semiconductor layer having impurity regions serving as a source regionand a drain region, a gate insulting layer, a gate electrode layerhaving a stacked layer structure including two layers, a sourceelectrode layer, and a drain electrode layer. The source electrode layeror drain electrode layer is in contact with and electrically connectedto an impurity region of the semiconductor layer and a pixel electrodelayer 630.

The source electrode layer and drain electrode layer have a stackedlayer structure, and the source electrode layer or drain electrodelayers 644 a and 644 b are electrically connected to the pixel electrodelayer 630 in an opening formed in an insulating layer 615. The openingformed in the insulating layer 615 can be formed by irradiation with alaser beam as shown in Embodiment Mode 2. In this embodiment mode, thesource electrode layer or drain electrode layer 644 b is formed using alow-melting point metal that is relatively easily evaporated (chromiumin this embodiment mode), and the source electrode layer or drainelectrode layer 644 a is formed using refractory metal that is noteasily evaporated compared to the source electrode layer or drainelectrode layer 644 b (tungsten in this embodiment mode). The sourceelectrode layer or drain electrode layers 644 a and 644 b areselectively irradiated with a laser beam from the insulating layer 615side, whereby an irradiated region of the source electrode layer ordrain electrode layer 644 b is evaporated by irradiation energy. Theinsulating layer 615 over the irradiated region of the source electrodelayer or drain electrode layer 644 b is removed, and the opening can beformed. The pixel electrode layer 630 is formed in the opening where thesource electrode layer or drain electrode layers 644 a or 644 b areexposed, and the source electrode layer or drain electrode layers 644 aand 644 b and the pixel electrode layer 630 can be electricallyconnected to each other.

The thin film transistor can be manufactured by various methods. Forexample, a crystalline semiconductor film is used as an active layer, agate electrode is formed over the crystalline semiconductor film with agate insulating film interposed therebetween, and an impurity element isadded to the active layer with use of the gate electrode. In such amanner, when the gate electrode is used for adding the impurity element,a mask for adding the impurity element does not need to be formed. Thegate electrode can have a single layer or stacked layer structure. Theimpurity region can be a high-concentration impurity region or alow-concentration impurity region with its concentration beingcontrolled. A structure of a thin film transistor having alow-concentration impurity region is called an LDD (Light Doped Drain)structure. Alternatively, the low-concentration impurity region may beoverlapped with the gate electrode and a structure of such a thin filmtransistor is called a GOLD (Gate Overlapped LDD) structure. Thepolarity of the thin film transistor becomes n-type when phosphorus (P)or the like is added to the impurity region. The polarity of the thinfilm transistor becomes p-type when boron (B) or the like is added.After that, insulating films 611 and 612 covering the gate electrode andthe like are formed. A dangling bond of the crystalline semiconductorfilm can be terminated by a hydrogen element mixed into the insulatingfilm 611(and the insulating 612).

In order to further improve planarity, the insulating layer 615 may beformed as an interlayer insulating layer. For the insulating layer 615,an organic material, an inorganic material, or a stacked layer structurethereof can be used. For example, a material such as silicon oxide,silicon nitride, silicon oxynitride, silicon nitride oxide, aluminumnitride, aluminum oxynitride, aluminum nitride oxide containing morenitrogen than oxygen, aluminum oxide, diamond-like carbon (DLC),polysilazane, nitrogen-containing carbon (CN), PSG (phosphosilicateglass), BPSG (borophosphosilicate glass), alumina, or a substancecontaining other inorganic insulating materials can be used.Alternatively, an organic insulating material may be used. As theorganic material, either a photosensitive or nonphotosensitive materialcan be used, and polyimide, acrylic, polyamide, polyimide amide, resist,benzocyclobutene, a siloxane resin, or the like can be used. It is to benoted that a siloxane resin is a resin containing a Si—O—Si bond. Theskeletal structure of siloxane is formed of a bond of silicon (Si) andoxygen (O). As a substituent, an organic group including at leasthydrogen (such as an alkyl group or an aryl goup) is used. As thesubstituent, a fluoro group may also be used. Alternatively, a fluorogroup and an organic group containing at least hydrogen may be used asthe substituent.

The pixel region and the driver circuit region can be formed over onesubstrate when the crystalline semiconductor film is used. In this case,a transistor in the pixel portion and a transistor in the driver circuitregion 608 b are formed at the same time. The transistor used in thedriver circuit region 608 b forms a CMOS circuit. A thin film transistorincluded in the CMOS circuit has a GOLD structure, but it may have anLDD structure like the transistor 622.

A structure of the thin film transistor in the pixel region is notlimited to those referred to in this embodiment mode and the thin filmtransistor in the pixel region may have a single gate structure in whichone channel formation region is formed, a double gate structure in whichtwo channel formation regions are formed, or a triple gate structure inwhich three channel formation regions are formed. A thin film transistorin a peripheral driver circuit region may also have a single gatestructure, a double gate structure, or a triple gate structure.

It is to be noted that a manufacturing method of a thin film transistoris not limited to those shown in this embodiment mode. The thin filmtransistor may have a top gate structure (such as a staggered type), abottom gate structure (such as a reverse staggered type), a dual gatestructure in which two gate electrode layers are arranged above or belowa channel formation region, each with a gate insulating film interposedtherebetween, or another structure.

Then, an insulating layer 631 called an alignment film is formed by aprinting method or a droplet discharging method to cover the pixelelectrode layer 630. It is to be noted that the insulating layer 631 canbe selectively formed by a screen printing method or an off-set printingmethod. Thereafter, rubbing treatment is performed. This rubbingtreatment does not need to be performed when a liquid crystal mode is,for example, a VA mode. An insulating layer 633 serving as an alignmentfilm is similar to the insulating layer 631. Then, the sealing material692 is formed in a peripheral region of the pixels by a dropletdischarging method.

After that, the counter substrate 695 provided with the insulating layer633 serving as the alignment film, a conductive layer 634 serving as acounter electrode, a colored layer 635 serving as a color filter, apolarizer 641 (also referred to as a polarizing plate), and a polarizer642 is attached to the substrate 600 which is a TFT substrate, with aspacer 637 interposed therebetween. A liquid crystal layer 632 isprovided in a space therebetween. Then, a polarizer (polarizing plate)643 is also provided on a side of the substrate 600, which is oppositeto a side where an element is formed since the liquid crystal displaydevice of this embodiment mode is a transmissive type. The polarizer canbe provided on the substrate with the use of an adhesive layer. A fillermay be mixed into the sealing material, and a shielding film (blackmatrix) or the like may be formed on the counter substrate 695. It is tobe noted that a color filter or the like may be formed of materialswhich exhibit red (R), green (G), and blue (B) when the liquid crystaldisplay device is a full-color display; and the colored layer may beomitted or may be formed of a material which exhibits at least onecolor, when the liquid crystal display device is a single-color display.

It is to be noted that when RGB light-emitting diodes (LEDs) or the likeare located in a backlight and a field sequential method which conductscolor display by time division is employed, there is a case where acolor filter is not provided. The black matrix may be provided so as tooverlap with the transistor and the CMOS circuit since the black matrixreduces the reflection of external light by the wiring in the transistorand the CMOS circuit. Alternatively, the black matrix may be provided tooverlap with the capacitor. It is because the black matrix can preventreflection due to a metal film included in the capacitor.

As a method for forming the liquid crystal layer, a dispenser method(dripping method) or an injection method in which the substrate 600provided with an element and the counter substrate 695 are attached anda liquid crystal is injected with the use of capillary phenomenon can beused. A dripping method may be employed when a large substrate to whichan injection method is difficult to be applied is used.

A spacer may be provided by a method in which particles each having asize of several tm are sprayed. In this embodiment mode, a method inwhich a resin film is formed over the entire surface of the substrateand then etched is employed. A material for the spacer is applied by aspinner and then, light exposure and developing treatment are carriedout so as to form a predetermined pattern. Further, the material isheated at 150 to 200° C. in a clean oven or the like to be hardened. Thespacer manufactured in such a manner can have various shapes dependingon the conditions of light exposure and the developing treatment. It ispreferable that the spacer have a columnar shape with a flat top so thatmechanical strength of the liquid crystal display device can be securedwhen the counter substrate is attached. The shape of the spacer is notparticularly limited and may be conic, pyramidal, or the like.

Then, in an external terminal connection region 602 which is adjacent toa wiring region 603, an FPC 694, which is a wiring board for connectionis provided over terminal electrode layers 678 a and 678 b electricallyconnected to the pixel region, with an anisotropic conductive layer 696interposed therebetween. The FPC 694 transmits a signal and potentialfrom an external portion. Through the foregoing steps, a liquid crystaldisplay device having a display function can be manufactured.

For the wiring, the gate electrode layer, the pixel electrode layer 630,and the conductive layer 634 serving as the counter electrode layer inthe transistor can be formed using indium tin oxide (ITO), indium zincoxide (IZO) in which zinc oxide (ZnO) is mixed with indium oxide, aconductive material in which silicon oxide (SiO₂) is mixed with indiumoxide, organic indium, organic tin, indium oxide containing tungstenoxide, indium zinc oxide containing tungsten oxide, indium oxidecontaining titanium oxide, indium tin oxide containing titanium oxide,or the like. Alternatively, a material such as a metal, e.g. tungsten(W), molybdenum (Mo), zirconium (Zr), hafnium (Hf), vanadium (V),niobium (Nb), tantalum (Ta), chromium (Cr), cobalt (Co), nickel (Ni),titanium (Ti), platinum (Pt), aluminum (Al), copper (Cu), or silver(Ag); an alloy of such metals; or metal nitride thereof can be used.

A retardation plate may be provided between the polarizing plate and theliquid crystal layer.

In this embodiment mode, a TN liquid crystal panel is shown; however,the above process can be similarly applied to liquid crystal panels ofother modes. For example, this embodiment mode can be applied to aliquid crystal panel of a horizontal electric field mode in which liquidcrystals are aligned parallel to the glass substrate by application ofan electric filed. Further, this embodiment mode can also be applied toa VA (Vertical Alignment) mode liquid crystal panel.

FIGS. 36 and 37 each show a pixel structure of a VA mode liquid crystalpanel. FIG. 36 is a top view, and a cross-sectional structure takenalong a line I-J is shown in FIG. 37. In the following description, bothof these drawings are used.

In this pixel structure, a plurality of pixel electrodes are provided inone pixel, and each pixel electrode is connected to a TFT. Each TFT isconstituted so as to be driven by a different gate signal. In otherwords, a multi-domain pixel has a structure in which a signal applied toeach pixel electrode is independently controlled.

A pixel electrode layer 1624 is connected to a TFT 1628 with a wiringlayer 1618 through an opening (contact hole) 1623. In addition, a pixelelectrode layer 1626 is connected to a TFT 1629 with a wiring layer 1619through an opening (contact hole) 1627. A gate wiring layer 1602 of theTFT 1628 and a gate electrode layer 1603 of the TFT 1629 are separatedso as to be able to receive different gate signals. On the other hand, awiring layer 1616 functioning as a data line is used by both the TFTs1628 and 1629.

The pixel electrode layers 1624 and 1626 are formed as in EmbodimentMode 1 by a droplet discharging step including two steps. Specifically,a first composition containing a conductive material is discharged alonga contour of a pattern of the pixel electrode layer by a first dropletdischarging step, and thus, a first conductive layer having aframe-shape is formed. A second composition containing a conductivematerial is discharged so as to fill inside the frame formed of thefirst conductive layer by a second droplet discharging step, and asecond conductive layer is formed. The first and second conductivelayers can be used as one continuous pixel electrode layer, whereby thepixel electrode layers 1624 and 1626 can be formed. As described above,since the process can be simplified and loss of materials can beprevented by the present invention, a display device can be manufacturedat low cost with high productivity.

The shapes of the pixel electrode layers 1624 and 1626 are different,and the pixel electrode layers 1624 and 1626 are separated by a slit1625. The pixel electrode layer 1626 is formed so as to surround thepixel electrode layer 1624 that is extended into a V-shape. Timings ofapplication of voltage to the pixel electrode layers 1624 and 1626 aremade different in the TFTs 1628 and 1629, whereby alignment of liquidcrystals are controlled. The TFT 1628 includes the gate wiring layer1602, a gate insulating layer 1606, a semiconductor layer 1608, asemiconductor layer 1610 having one conductivity type, a wiring layer1617 and a wiring layer 1618 over the substrate 1600. The TFT 1629includes the gate wiring layer 1603, the gate insulating layer 1606, asemiconductor layer 1609, a semiconductor layer 1611 having oneconductivity type, a wiring layer 1616 and a wiring layer 1619 over thesubstrate 1600. An insulating layer 1620 and an insulating layer 1622are formed over the wiring layers 1616, 1617, 1618 and 1619. Alight-shielding film 1632, a colored layer 1636, and a counter electrodelayer 1640 are formed on a counter substrate 1601. A planarizing film1637 is formed between the colored layer 1636 and the counter electrodelayer 1640 so that disordered alignment of liquid crystals of a liquidcrystal layer 1650 is prevented. FIG. 38 shows a structure on thecounter substrate side. The counter electrode layer 1640 is used bydifferent pixels in common, and a slit 1641 is formed. The slit 1641 andthe slit 1625 on the side of the pixel electrode layers 1624 and 1626are arranged so as to be alternately engaged with each other, and thus,an oblique electric field can be effectively generated and alignment ofliquid crystals can be controlled. Accordingly, an alignment directionof the liquid crystals is made varied depending on the place; therefore,the viewing angle can be widened. An alignment film 1648 is formed onthe pixel electrode layer 1626 and an aligment film 1646 is formed onthe counter electrode layer 1640.

As described above, a liquid crystal panel can be manufactured by usinga composite material, in which an organic compound and an inorganiccompound are mixed, as a pixel electrode layer. With the use of such apixel electrode layer, it is not necessary to use a transparentconductive film containing indium as its main component, and bottleneckof materials can be overcome.

This embodiment mode can be appropriately combined with Embodiment Mode1 or 2.

In accordance with the present invention, a component such as a wiringincluded in a display device can be formed into a desired shape. Inaddition, since complicated photolithography steps can be reduced and adisplay device can be manufactured through a simplified process, loss ofmaterials and the cost can be reduced. Therefore, a high performance andhighly reliable display device can be manufactured with a high yield.

Embodiment Mode 9

In this embodiment mode, an example of a highly reliable display devicewhich is manufactured through a simplified process at low cost will bedescribed. More specifically, a liquid crystal display device using aliquid crystal display element as a display element will be described.

In the display device shown in FIG. 18, over a substrate 250, in a pixelregion, a transistor 220 which is a reverse staggered thin filmtransistor, a pixel electrode layer 251, an insulating layer 252, aninsulating layer 253, a liquid crystal layer 254, a spacer 281, aninsulating layer 235, a counter electrode layer 256, a color filter 258,a black matrix 257, a counter substrate 210, a polarizing plate(polarizer) 231, and a polarizing plate (polarizer) 233 are provided;and in a sealing region, a sealing material 282, a terminal electrodelayer 287, an anisotropic conductive layer 288, and an FPC 286 areprovided.

A gate electrode layer, a source electrode layer, and a drain electrodelayer of the transistor 220 which is a reverse staggered thin filmtransistor formed in this embodiment mode are formed using a conductivelayer that is formed by a droplet discharging method as shown inEmbodiment Mode 1. Therefore, the process can be simplified, and loss ofmaterials can be prevented; therefore, a display device can bemanufactured at low cost with high productivity.

In this embodiment mode, a gate electrode layer, a source electrodelayer, a drain electrode layer, a wiring layer, a pixel electrode layer,and the like of the transistor 220 which is a reverse staggered thinfilm transistor included in the display device may also be formed bydischarging a liquid composition containing a material for forming theabove components in a plurality of steps as shown in Embodiment Mode 1.As shown in Embodiment Mode 1, a first conductive layer having aframe-shape is formed along the contour of the pattern of the conductivelayer by a first discharging step, and a second conductive layer isformed so as to fill inside the frame formed of the first conductivelayer by a second discharging step.

Therefore, when the first conductive layer (insulating layer) whichdetermines the contour of a formation region of the conductive layer(insulating layer) is formed by applying a composition with relativelyhigh viscosity and low wettability with respect to the formation region,a side edge portion which becomes a contour of a desired pattern can beformed with high controllability. When a composition with low viscosityand high wettability with respect to the formation region is appliedinside a frame formed of the first conductive layer (insulating layer),space, unevenness, and the like due to bubbles and the like in or on thesurface of the conductive layer are reduced, and a conductive layer(insulating layer) which is very flat and uniform can be formed.Therefore, by separate formation of an outer-side conductive layer(insulating layer) and an inner-side conductive layer (insulatinglayer), a conductive layer (insulating layer) that has a high level ofplanarity, less defects, and a desired pattern can be formed with highcontrollability. Accordingly, the process can be simplified, loss ofmaterials can be prevented, and the cost can be reduced.

In this embodiment mode, an amorphous semiconductor is used as asemiconductor layer, and a semiconductor layer having one conductivitytype may be formed as needed. In this embodiment mode, a semiconductorlayer and an amorphous n-type semiconductor layer as a semiconductorlayer having one conductivity type are stacked. Further, an NMOSstructure of an n-channel thin film transistor in which an n-typesemiconductor layer is formed, a PMOS structure of a p-channel thin filmtransistor in which a p-type semiconductor layer is formed, or a CMOSstructure of an n-channel thin film transistor and a p-channel thin filmtransistor can be manufactured.

Moreover, in order to impart conductivity, an element impartingconductivity is added by doping and an impurity region is formed in thesemiconductor layer; therefore, an n-channel thin film transistor and ap-channel thin film transistor can be formed. Instead of formation of ann-type semiconductor layer, conductivity may be imparted to thesemiconductor layer by plasma treatment with a PH₃ gas.

In this embodiment mode, the transistor 220 is an n-channel reversestaggered thin film transistor. In addition, a channel protective typereverse staggered thin film transistor in which a protective layer isprovided over the channel region of the semiconductor layer can also beused.

Next, a structure of a backlight unit 352 will be described. Thebacklight unit 352 includes a cold cathode tube, a hot cathode tube, alight-emitting diode, an inorganic EL element, or an organic EL elementas a light source 331 which emits light, a lamp reflector 332 toeffectively lead light to a light guide plate 335, the light guide plate335 by which light is totally reflected and led to the entire surface, adiffusing plate 336 for reducing variations in brightness, and areflective plate 334 for reusing light leaked under the light guideplate 335.

A control circuit for adjusting the luminance of the light source 331 isconnected to the backlight unit 352. The luminance of the light source331 can be controlled by a signal supplied from the control circuit.

A source electrode layer or drain electrode layer 232 of the transistor220 is electrically connected to the pixel electrode layer 251 in theopening formed in the insulating layer 252. The opening formed in theinsulating layer 252 can be formed by irradiation with a laser beam asshown in Embodiment Mode 2. In this embodiment mode, the sourceelectrode layer or drain electrode layer is formed using a low-meltingpoint metal that is relatively easily evaporated (chromium in thisembodiment mode). The source electrode layer or drain electrode layer isselectively irradiated with a laser beam from the insulating layer 252side, whereby part of an irradiated region of the source electrode layeror drain electrode layer is evaporated by irradiation energy. Theinsulating layer 252 over the irradiated region of the source electrodelayer or drain electrode layer is removed, and the opening can beformed. The pixel electrode layer 251 is formed in the opening where thesource electrode layer or drain electrode layer is exposed, and thesource electrode layer or drain electrode layer and the pixel electrodelayer 251 can be electrically connected to each other.

This embodiment mode can be appropriately combined with Embodiment Mode1 or 2.

In accordance with the present invention, a component such as a wiringincluded in a display device can be formed into a desired shape. Inaddition, since complicated photolithography steps can be reduced and adisplay device can be manufactured through a simplified process, loss ofmaterials and the cost can be reduced. Therefore, a high performance andhighly reliable display device can be manufactured with a high yield.

Embodiment Mode 10

In this embodiment mode, an example of a highly reliable display devicewhich is manufactured through a simplified process at low cost will bedescribed.

FIG. 21 shows an active matrix type electronic paper to which thepresent invention is applied. Although FIG. 21 shows an active matrixtype one, the present invention can also be applied to a passive matrixtype one.

A twist ball display system may be used for the electronic paper. Atwist ball display system means a method in which spherical particleseach colored in black and white are arranged between a first electrodelayer and a second electrode layer, and a potential difference isgenerated between the first electrode layer and the second electrodelayer so as to control directions of the spherical particles, so thatdisplay is performed.

A transistor 581 over a substrate 580 is a reverse coplanar type thinfilm transistor, and includes a gate electrode layer 582, a gateinsulating layer 584, wiring layers 585 a and 585 b, and a semiconductorlayer 586. In addition, the wiring layer 585 b is in contact with andelectrically connected to first electrode layers 587 a and 587 b throughan opening formed in an insulating layer 598. Between the firstelectrode layer 587 a and 587 b, and a second electrode layer 588 on acounter substrate 596, spherical particles 589 each including a blackregion 590 a and a white region 590 b are provided, and on the peripherythereof, a cavity 594 which is filled with liquid, is provided. Thecircumference of the spherical particle 589 is filled with a filler 595such as resin or the like (refer to FIG. 21).

In this embodiment mode, a gate electrode layer, a semiconductor layer,a source electrode layer, a drain electrode layer, a wiring layer, afirst electrode layer, and the like included in the display device mayalso be formed by discharging a liquid composition containing a materialfor forming the above components in a plurality of steps as shown inEmbodiment Mode 1. As shown in Embodiment Mode 1, a first conductivelayer having a frame-shape is formed along the contour of the pattern ofthe conductive layer by a first discharging step, and a secondconductive layer is formed so as to fill inside the frame formed of thefirst conductive layer by a second discharging step.

Therefore, when the first conductive layer (insulating layer) whichdetermines the contour of a formation region of the conductive layer(insulating layer) is formed by applying a composition with relativelyhigh viscosity and low wettability with respect to the formation region,a side edge portion which becomes a contour of a desired pattern can beformed with high controllability. When a liquid composition with lowviscosity and high wettability with respect to the formation region isapplied inside a frame formed of the first conductive layer (insulatinglayer), space, unevenness, and the like due to bubbles and the like inor on the surface of the conductive layer are reduced, and a conductivelayer (insulating layer) which is very flat and uniform can be formed.Therefore, by separate formation of an outer-side conductive layer(insulating layer) and an inner-side conductive layer (insulatinglayer), a conductive layer (insulating layer) that has a high level ofplanarity, less defects, and a desired pattern can be formed with highcontrollability. Accordingly, the process can be simplified, loss ofmaterials can be prevented, and the cost can be reduced.

The wiring layer 585 b is electrically connected to the first electrodelayer 587 a in the opening formed in the insulating layer 598. Theopening formed in the insulating layer 598 can be formed by irradiationwith a laser beam as shown in Embodiment Mode 2. In this embodimentmode, the wiring layer 585 b is formed using a low-melting point metalthat is relatively easily evaporated (chromium in this embodiment mode).The wiring layer 585 b is selectively irradiated with a laser beam fromthe insulating layer 598 side, whereby part of an irradiated region ofthe wiring layer 585 b is evaporated by irradiation energy. Theinsulating layer 598 over the irradiated region of the wiring layer 585b is removed, and the opening can be formed. The first electrode layer587 a is formed in the opening where the wiring layer 585 b is exposed,and the wiring layer 585 b and the first electrode layer 587 a can beelectrically connected to each other.

Further, instead of the twist ball, an electrophoretic element can alsobe used. A microcapsule having a diameter of 10 to 20 μm which is filledwith transparent liquid, positively charged white microparticles, andnegatively charged black microparticles and sealed, is used. In themicrocapsule which is provided between the first electrode layer and thesecond electrode layer, when an electric field is applied by the firstelectrode layer and the second electrode layer, the white microparticlesand black microparticles move to opposite sides from each other, so thatwhite or black can be displayed. A display element using this principleis an electrophoretic display element, and is called an electronic paperin general. The electrophoretic display element has higher reflectivitythan a liquid crystal display element, and thus, an assistant light isunnecessary, power consumption is low, and a display portion can berecognized also in a dusky place. Even when electric power is notsupplied to the display portion, an image which has been displayed oncecan be stored. Thus, a displayed image can be stored even if a displaydevice having a display function is distanced from a source of anelectronic wave.

The transistor may have any structure as long as the transistor canserve as a switching element. As a semiconductor layer, varioussemiconductors such as an amorphous semiconductor, a crystallinesemiconductor, a polycrystalline semiconductor, and a microcrystalsemiconductor can be used, or an organic transistor may be formed usingan organic compound.

In this embodiment mode, specifically, a case where a structure of adisplay device is an active matrix type is shown; however, of course,the present invention can also be applied to a passive matrix displaydevice. Also in a passive matrix display device, a wiring layer, anelectrode layer, an insulating layer, and the like may be formed by aplurality of selective discharging steps as in Embodiment Mode 1; thus,a conductive layer and an insulating layer formed into a precise andfavorable shape can be formed.

This embodiment mode can be appropriately combined with Embodiment Mode1 or 2.

In accordance with the present invention, a component such as a wiringincluded in a display device can be formed into a desired shape. Inaddition, since complicated photolithography steps can be reduced and adisplay device can be manufactured through a simplified process, loss ofmaterials and the cost can be reduced. Therefore, a high performance andhighly reliable display device can be manufactured with a high yield.

Embodiment Mode 11

Next, a mode of mounting a driver circuit on a display panelmanufactured in accordance with Embodiment Modes 3 to 10 will bedescribed.

First, a display device employing a COG method will be described withreference to FIG. 26A. A pixel portion 2701 and a protective circuit2713 for displaying information of characters, images, or the like isprovided over a substrate 2700. A substrate provided with a plurality ofdriver circuits is divided into rectangles, and a driver circuit 2751after division (also referred to as a driver IC) is mounted on thesubstrate 2700. FIG. 26A shows a mode of mounting a plurality of driverICs 2751 and FPCs 2750 on the ends of driver ICs 2751. In addition, thesize obtained by division may be made almost the same as the length of aside of the pixel portion on a signal line side, and a tape may bemounted on the end of the single driver IC.

Alternatively, a TAB method may be employed. In that case, a pluralityof tapes may be attached, and driver ICs may be mounted on the tapes asshown in FIG. 26B. Similarly to the case of a COG method, a singledriver IC may be mounted on a single tape. In this case, a metal pieceor the like for fixing the driver IC may be attached together in termsof the strength.

A plurality of driver ICs to be mounted on the display panel arepreferably formed over a rectangular substrate having a side of 300 to1000 mm or a side longer than 1000 mm for improvement in productivity.

In other words, a plurality of circuit patterns each including a drivercircuit portion and an input-output terminal as a unit may be formedover a substrate and may be divided to be used. In consideration of theside length of the pixel portion or the pixel pitch, the driver IC maybe formed to be a rectangle having a long side of 15 to 80 mm and ashort side of 1 to 6 mm. Alternatively, the driver IC may be formed tohave the side length that is the same as that of the pixel portion, orthe length obtained by adding a side length of the pixel portion and aside length of each driver circuit.

An advantage of the external dimension of the driver IC over an IC chipis the length of the long side. When the driver IC having a long sidelength of 15 to 80 mm is used, the number of the driver ICs necessaryfor being mounted in accordance with the pixel portion is smaller thanthat in the case of using an IC chip. Therefore, a yield inmanufacturing can be improved. When a driver IC is formed over a glasssubstrate, there is no limitation on the shape of the substrate used asa base; therefore, productivity is not decreased. This is a greatadvantage compared to the case where IC chips are taken out of acircular silicon wafer.

When a scanning line driver circuit 3702 is formed to be integrated overa substrate as shown in FIG. 25B, a driver IC provided with a signalline driver circuit is mounted on a region on the outer side of a pixelportion 3701. The driver IC is a signal line driver circuit. In order toform a pixel portion corresponding to RGB full color, 3072 signal linesare necessary for an XGA class and 4800 signal lines are necessary for aUXGA class. The signal lines formed in such a number are divided intoseveral blocks at the end portion of the pixel portion 3701, and leadinglines are formed. The signal lines are gathered corresponding to thepitches of output terminals of the driver ICs.

The driver IC is preferably formed using a crystalline semiconductorformed over a substrate. The crystalline semiconductor is preferablyformed by being irradiated with a continuous wave laser beam. Therefore,a continuous wave solid-state or gas laser is used for an oscillator forgenerating the laser beam. There are few crystal defects when acontinuous wave laser is used, and as a result, a transistor can bemanufactured using a polycrystalline semiconductor layer having a largegrain size. In addition, high-speed driving is possible since mobilityand response speed are favorable, and it is possible to further improvean operating frequency of an element than that of the conventionalelement. Therefore, high reliability can be obtained since there islittle variation in characteristics. It is to be noted that a channellength direction of the transistor and a moving direction of a laserbeam over the substrate are preferably arranged in the same direction inorder to further improve the operating frequency. This is because thehighest mobility can be obtained when a channel length direction of atransistor and a moving direction of a laser beam over a substrate arealmost parallel to each other (preferably, −30° to 30°) in a step oflaser crystallization with a continuous wave laser. It is to be notedthat the channel length direction corresponds to a current-flowingdirection, in other words, a direction in which electric charge moves ina channel formation region. The thus manufactured transistor has anactive layer including a polycrystalline semiconductor layer in whichcrystal grains are extended in the channel length direction, and thismeans that crystal grain boundaries are formed almost along the channellength direction.

In order to perform laser crystallization, it is preferable tosignificantly narrow the laser beam, and the shape of the laser beam(beam spot) preferably has the width that is the same as a short side ofthe driver ICs, which is greater than or equal to 1 mm and less than orequal to 3 mm. In addition, in order to secure an enough and effectiveenergy density for an object to be irradiated, an irradiated region withthe laser beam preferably has a linear shape. The term “linear” usedherein refers to not a line in a strict sense but a rectangle or anoblong with a large aspect ratio. For example, the linear shape refersto a rectangle or an oblong with an aspect ratio of greater than orequal to 2 (preferably greater than or equal to 10 and less than orequal to 10000). Thus, by making a width of the laser beam shape (beamspot) the same length as a short side of the driver ICs, a method formanufacturing a display device, of which productivity is improved, canbe provided.

As shown in FIGS. 26A and 26B, driver ICs may be mounted as both thescanning line driver circuit and the signal line driver circuit. In thiscase, it is preferable to use the driver ICs having differentspecifications for the scanning line driver circuit and the signal linedriver circuit.

In the pixel portion, the signal line and the scanning line intersect toform a matrix, and a transistor is arranged at a portion correspondingto each intersection. One feature of the present invention is that TFTshaving an amorphous semiconductor or a semi-amorphous semiconductor as achannel portion are used as the transistors arranged in the pixelportion. The amorphous semiconductor is formed by a method such as aplasma CVD method or a sputtering method. The semi-amorphoussemiconductor can be formed by a plasma CVD method at temperatures ofless than or equal to 300° C. A film thickness enough to form thetransistor is formed in a short time even in the case of using, forexample, a non-alkaline glass substrate having an external size of 550mm×650 mm. The feature of such a manufacturing technique is effective inmanufacturing a large-sized display device. In addition, asemi-amorphous TFl can obtain field effect mobility of 2 to 10 cm²/V·secby formation of a channel formation region using a SAS. When the presentinvention is applied, a minute wiring can be stably formed without adefect such as a short circuit since a pattern can be formed into adesired shape with high controllability. Thus, a display panel in whichsystem-on-panel is realized can be manufactured.

The scanning line driver circuit can also be formed to be integratedover the substrate with the use of a TFT having a semiconductor layerformed of a SAS. When a TFT having a semiconductor layer formed of an ASis used, the driver ICs may be mounted as both the scanning line drivercircuit and the signal line driver circuit.

In that case, it is preferable to use the driver ICs having differentspecifications for the scanning line driver circuit and the signal linedriver circuit. For example, a transistor included in the scanning linedriver IC is required to withstand a voltage of approximately 30 V;however, since a drive frequency is less than or equal to 100 kHz,high-speed operation is not required relatively. Therefore, it ispreferable to set a channel length (L) of the transistor included in thescanning line driver sufficiently long. On the other hand, a transistorof the signal line driver IC is required to withstand a voltage of onlyapproximately 12 V; however, since a drive frequency is around 65 MHz at3 V, high-speed operation is required. Therefore, it is preferable toset a channel length or the like of the transistor included in a driveron a micron rule.

A method for mounting the driver IC is not particularly limited, and aCOG method, a wire bonding method, or a TAB method can be employed.

When the thicknesses of the driver IC and the counter substrate are setequal to each other, the heights of the driver IC and the countersubstrate are almost equal, which contributes to thinning of a displaydevice as a whole. When both substrates are formed from the samematerial, thermal stress is not generated and characteristics of acircuit formed from a TFT are not damaged even when a temperature changeis caused in the display device. Furthermore, the number of the driverICs to be mounted for one pixel portion can be reduced by mountingdriver ICs having a longer side than IC chips as driver circuits asshown in this embodiment mode.

As described above, a driver circuit can be incorporated into a displaypanel.

Embodiment Mode 12

The following will describe an example of a display panel (an EL displaypanel or a liquid crystal display panel) manufactured in accordance withEmbodiment Modes 3 to 10, in which a semiconductor layer is formed usingan amorphous semiconductor or SAS and a scanning line driver circuit isformed over a substrate.

FIG. 32 is a block diagram of a scanning line driver circuit formedusing an n-channel TFT that uses an SAS with an electron field-effectmobility of 1 to 15 cm²/V·sec.

In FIG. 32, a block 8500 corresponds to a pulse output circuitoutputting sampling pulses for one stage. A shift register includes nnumber of pulse output circuits. Reference numeral 8501 denotes a buffercircuit and a pixel 8502 is connected to the buffer circuit.

FIG. 33 shows a specific configuration of the pulse output circuit 8500,where the circuit includes n-channel TFTs 8601 to 8613. In this case,the sizes of the TFTs may be determined in consideration of operationcharacteristics of the n-channel TFTs using an SAS. For example, whenthe channel length is set to be 8 μm, the channel width can be set to bein the range of 10 to 80 μm.

Further, a specific configuration of the buffer circuit 8501 is shown inFIG. 34. Similarly, the buffer circuit includes n-channel TFTs 8620 to8635. In this case, the sizes of the TFTs may be determined inconsideration of operation characteristics of the n-channel TFTs usingan SAS. For example, when the channel length is set to be 10 μm, thechannel width can be set to be in the range of 10 to 1800 μm.

In order to realize such a circuit, TFTs are necessary to be connectedto one another with a wiring.

As described above, a driver circuit can be incorporated into a displaypanel.

Embodiment Mode 13

This embodiment mode will be described with reference to FIG. 16. FIG.16 shows an example in which an EL display module is formed using a TFTsubstrate 2800 which is manufactured by the present invention. In FIG.16, a pixel portion including pixels is formed over the TFT substrate2800.

In FIG. 16, outside the pixel portion, a protective circuit portion 2801is provided between a driver circuit and the pixel. The protectivecircuit portion 2801 may be provided with a TFT similar to that formedin a pixel. Alternatively, the protective circuit portion 2801 mayoperate similarly to a diode by connecting a gate and a source or adrain of such a TFT. A driver IC formed using a single crystallinesemiconductor, a stick driver IC formed using a polycrystallinesemiconductor film over a glass substrate, a driver circuit formed usingan SAS, or the like is applied to a driver circuit 2809.

The TFT substrate 2800 is attached firmly to a sealing substrate 2820with spacers 2806 a and 2806 b formed by a droplet discharging methodinterposed therebetween. The spacers are preferably provided to keep adistance between two substrates constant even when the substrate is thinor an area of the pixel portion is enlarged. A space between the TFTsubstrate 2800 and the sealing substrate 2820 over light-emittingelements 2804 and 2805 connected to TFTs 2802 and 2803, respectively,may be filled with a resin material having at least a light-transmittingproperty of visible light, and the resin material may be solidified.Alternatively, the space may be filled with anhydrous nitrogen or aninert gas.

In this embodiment mode, a gate electrode layer, a semiconductor layer,a source electrode layer, a drain electrode layer, a wiring layer, afirst electrode layer, and the like included in the display device maybe formed by discharging a liquid composition containing a material forforming the above components in a plurality of steps as shown inEmbodiment Mode 1. As shown in Embodiment Mode 1, a first conductivelayer having a frame-shape is formed along the contour of the pattern ofthe conductive layer by a first discharging step, and a secondconductive layer is formed so as to fill inside the frame formed of thefirst conductive layer by a second discharging step.

Therefore, when the first conductive layer (insulating layer) whichdetermines the contour of a formation region of the conductive layer(insulating layer) is formed by applying a composition with relativelyhigh viscosity and low wettability with respect to the formation region,a side edge portion which becomes a contour of a desired pattern can beformed with high controllability. When a liquid composition with lowviscosity and high wettability with respect to the formation region isapplied inside a frame formed of the first conductive layer (insulatinglayer), space, unevenness, and the like due to bubbles and the like inor on the surface of the conductive layer are reduced, and a conductivelayer (insulating layer) which is very flat and uniform can be formed.Therefore, by separate formation of an outer-side conductive layer(insulating layer) and an inner-side conductive layer (insulatinglayer), a conductive layer (insulating layer) that has a high level ofplanarity, less defects, and a desired pattern can be formed with highcontrollability. Therefore, the process can be simplified, loss ofmaterials can be prevented, and the cost can be reduced.

FIG. 16 shows a case where the light-emitting elements 2804 and 2805 aretop emission type, which emit light in the direction of arrows shown inthe drawing. Multicolor display can be performed by making each pixel toemit light of a different color of red, green, or blue. At this time,color purity of light emitted to an external portion can be improved byformation of colored layers 2807 a, 2807 b, and 2807 c corresponding torespective colors on the sealing substrate 2820 side. Moreover, pixelswhich emit white light may be used and combined with the colored layers2807 a, 2807 b, and 2807 c.

The driver circuit 2809 which is an external circuit is connected to ascanning line connection terminal or a signal line connection terminalwhich is provided at one end of an external circuit board 2811 through awiring board 2810. In addition, a heat pipe 2813 which is a highlyefficient thermal conductive device with a pipe shape and a heat sink2812, which are used for radiating heat to the external portion of thedevice, may be provided in contact with or adjacent to the TFT substrate2800 to increase a heat radiation effect.

It is to be noted that FIG. 16 shows the top emission EL module;however, a bottom emission module may be employed by changing thestructure of the light-emitting element or the arrangement of theexternal circuit board. Of course, a dual emission module in which lightis emitted from both sides of the top and bottom surfaces may be used.In the case of top emission, an insulating layer serving as a partitionwall may be colored and used as a black matrix. This partition wall canbe formed by a droplet discharging method, and it may be formed bymixing a black resin of a pigrnent material, carbon black, or the likeinto a resin material such as polyimide. A stacked layer thereof mayalso be used.

In addition, in an EL display module, reflected light of light enteringfrom an external portion may be blocked with the use of a retardationplate or a polarizing plate. In a top emission display device, aninsulating layer serving as a partition wall may be colored and used asa black matrix. This partition wall can be formed by a dropletdischarging method or the like. Carbon black or the like may be mixedinto a black resin of a pigment material or a resin material such aspolyimide to be used, and a stacked layer thereof may also be used. By adroplet discharging method, different materials may be discharged to thesame region plural times to form the partition wall. A quarter waveplate or a half wave plate may be used as the retardation plate and maybe designed to be able to control light. As the structure, thelight-emitting element, the sealing substrate (sealing material), theretardation plate (quarter wave plate (λ/4) or half wave plate (λ/2)),and the polarizing plate are sequentially formed over a TFT elementsubstrate, and light emitted from the light-emitting element istransmitted therethrough and emitted to an external portion from thepolarizing plate side. The retardation plate or polarizing plate may-beprovided on a side to which light is emitted or may be provided on bothsides in the case of a dual emission display device in which light isemitted from the both surfaces. In addition, an anti-reflective film maybe provided on the outer side of the polarizing plate. Accordingly,higher-definition and precise images can be displayed.

As for the TFT substrate 2800, a sealing structure may be formed byattaching a resin film to the side where the pixel portion is formed,with the use of a sealing material or an adhesive resin. Although glasssealing using a glass substrate is shown in this embodiment mode,various sealing methods such as resin sealing using a resin, plasticsealing using plastics, and film sealing using a film can be adopted. Agas barrier film which prevents water vapor from penetrating the resinfilm is preferably provided over the surface of the resin film. Byemploying a film sealing structure, further reduction in thickness andweight can be achieved.

This embodiment mode can be combined with any of Embodiment Modes 1 to7, 11, and 12.

Embodiment Mode 14

This embodiment mode will be described with reference to FIGS. 20A ant20B. FIGS. 20A and 20B show an example in which a liquid crystal displaymodule is formed using a TFT substrate 2600 manufactured in accordancewith the present invention.

FIG. 20A is an example of a liquid crystal display module. The TFTsubstrate 2600 and a counter substrate 2601 are firmly attached to eachother with a sealing material 2602, and a pixel portion 2603 and aliquid crystal layer 2604 are provided therebetween, whereby a displayregion is formed. A colored layer 2605 is necessary for performing colordisplay, and colored layers corresponding to red, green, and blue areprovided for each pixel in the case of RGB mode. A polarizing plate 2606is provided outside the counter substrate 2601, and a polarizing plate2607 and a diffusing plate 2613 are provided outside the TFT substrate2600. A light source includes a cold cathode tube 2610 and a reflectiveplate 2611, and a circuit substrate 2612 is connected to a wiringcircuit portion 2608 of the TFT substrate 2600 through a flexible wiringboard 2609 and includes an external circuit such as a control circuitand a power source circuit. In addition, a retardation plate may bestacked between the polarizing plate and the liquid crystal layer.

For the liquid crystal display module, a TN (Twisted Nematic) mode, anIPS (In-Plane-Switching) mode, an FFS (Fringe Field Switching) mode, anMVA (Multi-domain Vertical Alignment) mode, a PVA (Patterned VerticalAlignment) mode, an ASM (Axially Symmetric aligned Micro-cell) mode, anOCB (Optical Compensated Birefringence) mode, an FLC (FerroelectricLiquid Crystal) mode, an AFLC (AntiFerroelectric Liquid Cryatl), or thelike can be used.

FIG. 20B shows an example of an FS-LCD (Field Sequential-LCD) in whichan OCB mode is applied to the liquid crystal display module of FIG. 20A.The FS-LCD emits light of red, green, and blue during one frame periodand can perform color display by combining images using time division.Since light of each color is emitted by a light-emitting diode, a coldcathode tube, or the like, a color filter is not necessary. Thus, it isnot necessary to arrange color filters of three primary colors andrestrict the display region of each color, and display of all threecolors can be performed in any region. Meanwhile, since light of threecolors is emitted during one frame period, high-speed response isrequired for a liquid crystal. By employing an FLC mode liquid crystallayer, an OCB mode liquid crystal layer, or the like using an FS methodto a display device of the present invention, a display device or aliquid crystal television set with high performance and high imagequality can be completed.

A liquid crystal layer of an OCB mode has a so-called π-cell structure.In the π-cell structure, liquid crystal molecules are aligned so thattheir pretilt angles are plane-symmetric along a center plane between anactive matrix substrate and a counter substrate. An orientation state ofa liquid crystal of a π-cell structure is splay-orientation when avoltage is not applied between the substrates, and then shifts tobend-orientation when a voltage is applied therebetween. In this bendorientation state, white display is obtained. When a voltage is appliedfurther, liquid crystal molecules of bend-orientation get orientatedperpendicular to the both substrates so that light is not transmitted.With the OCB mode, response with about 10-times-higher speed than aconventional TN mode can be achieved.

Moreover, as a mode for the FS method, an HV (Half-V)-FLC or an SS(Surface stabilized)-FLC using a ferroelectric liquid crystal (FLC)capable of high-speed operation, or the like can also be used. The OCBmode uses a nematic liquid crystal having relatively low viscosity,while the HV-FLC or the SS-FLC uses a smectic liquid crystal having aferroelectric phase.

Moreover, optical response speed of a liquid crystal display module getshigher by narrowing the cell gap of the liquid crystal display module.In addition, the optical response speed can also get higher bydecreasing the viscosity of the liquid crystal material. The increase inresponse speed is particularly advantageous when a pixel pitch in apixel portion of a TN mode liquid crystal display module is less than orequal to 30 μm. Also, further increase in response speed is possible byan overdrive method in which applied voltage is increased (or decreased)for a moment.

FIG. 20B shows a transmissive liquid crystal display module, in which ared light source 2910 a, a green light source 2910 b, and a blue lightsource 2910 c are provided as light sources. The light sources areprovided with a control portion 2912 in order to switch on or off thered light source 2910 a, the green light source 2910 b, and the bluelight source 2910 c. The control portion 2912 controls light emission ofeach color, light enters the liquid crystal, and images are combinedwith the use of time division, whereby color display is performed.

As described above, a high definition and highly reliable liquid crystaldisplay module can be manufactured with the use of the presentinvention.

This embodiment mode can be combined with any of Embodiment Modes 1, 2,8, 9, 11, and 12.

Embodiment Mode 15

A television set (also referred to as simply a TV or a televisionreceiver) can be completed using a display device formed in accordancewith the present invention. FIG. 27 is a block diagram showing a mainstructure of a television set.

FIG. 25A is a top view showing a structure of a display panel inaccordance with the present invention. A pixel portion 2701 in whichpixels 2702 are arranged in matrix, a scanning line input terminal 2703,and a signal line input terminal 2704 are formed over a substrate 2700having an insulating surface. The number of pixels may be determined inaccordance with various standards. In the case of XGA of RGB full colordisplay, the number of pixels may be 1024×768×3 (RGB). In the case ofUXGA of RGB full color display, the number of pixels may be 1600×1200×3(RGB), and in the case of full-spec high-definition RGB full colordisplay, the number of pixels may be 1920×1080×3 (RGB).

The pixels 2702 are formed in a matrix by intersections of scanninglines extended from the scanning line input terminal 2703 and signallines extended from the signal line input terminal 2704. Each pixel 2702in the pixel portion 2701 is provided with a switching element and apixel electrode layer connected to the switching element. A typicalexample of the switching element is a TFT. The gate electrode layer sideof the TFT is connected to a scanning line, and a source or drain sideof the TFT is connected to a signal line, which enables each pixel to beindependently controlled by a signal input from an external portion.

FIG. 25A shows a structure of a display panel in which a signal to beinput to a scanning line and a signal line is controlled by an externaldriver circuit. Alternatively, a driver IC 2751 may be mounted on thesubstrate 2700 by a COG (Chip on Glass) method as shown in FIG. 26A. Asanother mounting mode, a TAB (Tape Automated Bonding) method may also beused as shown in FIG. 26B. The driver IC may be formed over a singlecrystal semiconductor substrate or may be formed with a TFT over a glasssubstrate. In FIGS. 26A and 26B, the driver IC 2751 is connected to anFPC (flexible printed circuit) 2750.

When a TFT provided in a pixel is formed from a semiconductor havingcrystallinity, a scanning line driver circuit 3702 can be formed over asubstrate 3700 as shown in FIG. 25B. In FIG. 25B, a pixel portion 3701is controlled by an external driver circuit connected to a signal lineinput terminal 3704 as in FIG. 25A. When a TFT in a pixel is formed froma polycrystalline (microcrystalline) semiconductor, a single crystalsemiconductor, or the like having high mobility, a pixel portion 4701, ascanning line driver circuit 4702, and a signal line driver circuit 4704can be formed to be integrated over a glass substrate 4700 as shown inFIG. 25C.

In FIG. 27, a display panel can be formed in any mode as follows: as thestructure shown in FIG. 25A, only a pixel portion 901 is formed, and ascanning line driver circuit 903 and a signal line driver circuit 902are mounted by a TAB method as shown in FIG. 26B or by a COG method asshown in FIG. 26A; a TFT is formed, and a pixel portion 901 and ascanning line driver circuit 903 are formed to be integrated over asubstrate, and a signal line driver circuit 902 is separately mounted asa driver IC as shown in FIG. 25B; a pixel portion 901, a signal linedriver circuit 902, and a scanning line driver circuit 903 are formed tobe integrated over the substrate as shown in FIG. 25C; and the like.

In FIG. 27, as a structure of other external circuits, a video signalamplifier circuit 905 that amplifies a video signal among signalsreceived by a tuner 904, a video signal processing circuit 906 thatconverts the signals output from the video signal amplifier circuit 905into chrominance signals corresponding to each color of red, green, andblue, a control circuit 907 that converts the video signal so as to beinput to a driver IC, and the like are provided on an input side of thevideo signal. The control circuit 907 outputs signals to both a scanningline side and a signal line side. In the case of digital driving, asignal dividing circuit 908 may be provided on the signal line side andan input digital signal may be divided into m pieces to be supplied.

Among signals received by the tuner 904, an audio signal is transmittedto an audio signal amplifier circuit 909, and the output thereof issupplied to a speaker 913 through an audio signal processing circuit910. A control circuit 911 receives control information on a receivingstation (a receiving frequency) or sound volume from an input portion912 and transmits the signal to the tuner 904 or the audio signalprocessing circuit 910.

A television set can be completed by incorporating the display moduleinto a chassis as shown in FIGS. 28A and 28B. When a liquid crystaldisplay module is used as a display module, a liquid crystal televisionset can be manufactured. When an EL display module is used, an ELtelevision set can be manufactured. Alternatively, a plasma television,electronic paper, or the like can be manufactured. In FIG. 28A, a mainscreen 2003 is formed by using the display module, and a speaker portion2009, an operation switch, and the like are provided as its accessoryequipment. Thus, a television set can be completed in accordance withthe present invention.

A display panel 2002 is incorporated into a chassis 2001. With the useof a receiver 2005, in addition to reception of general TV broadcast,information communication can also be carried out in one way (from atransmitter to a receiver) or in two ways (between a transmitter and areceiver or between receivers) by connection to a communication networkby a fixed line or wirelessly through a modem 2004. The operation of thetelevision set can be carried out by switches incorporated in thechassis or by a remote control device 2006, which is separated from themain body. A display portion 2007 that displays information to be outputmay also be provided in this remote control device.

In addition, in the television set, a structure for displaying achannel, sound volume, or the like may be additionally provided byformation of a sub-screen 2008 with a second display panel in additionto the main screen 2003. In this structure, the main screen 2003 and thesub-screen 2008 can be formed using a liquid crystal display panel ofthe present invention. Alternatively, the main screen 2003 may be formedusing an EL display panel superior in viewing angle, and the sub-screen2008 may be formed using a liquid crystal display panel capable ofdisplay with low power consumption. In order to prioritize low powerconsumption, a structure in which the main screen 2003 is formed using aliquid crystal display panel, the sub-screen 2008 is formed using an ELdisplay panel, and the sub-screen is able to flash on and off may alsobe employed. In accordance with the present invention, a highly reliabledisplay device can be manufactured even by using such a large substratewith many TFTs and electronic parts.

FIG. 28B shows a television set having a large display portion, e.g.20-inch to 80-inch display portion, which includes a chassis 2010, adisplay portion 2011, a remote control device 2012 which is an operationportion, a speaker portion 2013, and the like. The present invention isapplied to manufacture the display portion 2011. The television setshown in FIG. 28B is a wall-hanging type, and does not require a widespace.

Of course, the present invention is not limited to the television setand is also applicable to various usages such as display mediums havinga large area, for example, a monitor of a personal computer, aninformation display board at a train station, an airport, or the like,or an advertisement display board on the street.

This embodiment mode can be appropriately combined with any ofEmbodiment Modes 1 to 14.

Embodiment Mode 16

Electronic devices of the present invention include: television sets(also simply referred to as TVs or television receivers), cameras suchas digital cameras and digital video cameras, mobile phone sets (alsosimply referred to as cellular phone sets or cellular phones), portableinformation terminals such as a PDA, portable game machines, monitorsfor computers, computers, audio reproducing devices such as car audiosets, image reproducing devices provided with a recording medium such ashome-use game machines, and the like. Specific examples thereof will bedescribed with reference to FIGS. 29A to 29E.

A portable information terminal shown in FIG. 29A includes a main body9201, a display portion 9202, and the like. The display device of thepresent invention can be applied to the display portion 9202. As aresult, since the display device of the present invention can bemanufactured through a simplified process at low cost, a portableinformation terminal which is highly reliable can be provided at lowcost.

A digital video camera shown in FIG. 29B includes a display portion9701, a display portion 9702, and the like. The display device of thepresent invention can be applied to the display portion 9701. As aresult, since the display device of the present invention can bemanufactured through a simplified process at low cost, a digital videocamera which is highly reliable can be provided at low cost.

A cellular phone set shown in FIG. 29C includes a main body 9101, adisplay portion 9102, and the like. The display device of the presentinvention can be applied to the display portion 9102. As a result, sincethe display device of the present invention can be manufactured througha simplified process at low cost, a cellular phone set which is highlyreliable can be provided at low cost.

A portable television set shown in FIG. 29D includes a main body 9301, adisplay portion 9302, and the like. The display device of the presentinvention can be applied to the display portion 9302. As a result, sincethe display device of the present invention can be manufactured througha simplified process at low cost, a portable television set which ishighly reliable can be provided at low cost. The display device of thepresent invention can be applied to various types of television setsincluding a small-sized television mounted on a portable terminal suchas a cellular phone set, a medium-sized television that is portable, anda large-sized television (for example, 40 inches or more in size).

A portable computer shown in FIG. 29E includes a main body 9401, adisplay portion 9402, and the like. The display device of the presentinvention can be applied to the display portion 9402. As a result, sincethe display device of the present invention can be manufactured througha simplified process at low cost, a portable computer which is highlyreliable can be provided at low cost.

As described above, with the use of the display device of the presentinvention, high performance electronic devices that can display an imagewith high quality and excellent visibility can be provided.

This embodiment mode can be appropriately combined with any ofEmbodiment Modes 1 to 15.

This application is based on Japanese Patent Application serial no.2006-184719 filed in Japan Patent Office on Jul. 4, 2006, the entirecontents of which are hereby incorporated by reference.

1. A method for manufacturing a semiconductor device comprising thesteps of: forming a first conductive layer having a frame-shape over asubstrate having an insulating surface by discharging a firstcomposition containing a conductive material; and forming a secondconductive layer by discharging a second composition containing aconductive material in a region surrounded by the first conductive layerhaving the frame-shape.
 2. The method for manufacturing a semiconductordevice according to claim 1, wherein the first composition containingthe conductive material is continuously discharged, and the secondcomposition containing the conductive material is intermittentlydischarged.
 3. The method for manufacturing a semiconductor deviceaccording to claim 1, wherein a thickness of the first conductive layeris larger than a thickness of the second conductive layer.
 4. The methodfor manufacturing a semiconductor device according to claim 1, wherein apixel electrode layer includes the first conductive layer and the secondconductive layer.
 5. A method for manufacturing a semiconductor devicecomprising the steps of: forming a first conductive layer having aframe-shape over a substrate having an insulating surface by discharginga first composition containing a conductive material; and forming asecond conductive layer by discharging a second composition containing aconductive material in a region surrounded by the first conductive layerhaving the frame-shape, wherein viscosity of the first compositioncontaining the conductive material is higher than viscosity of thesecond composition containing the conductive material.
 6. The method formanufacturing a semiconductor device according to claim 5, wherein thefirst composition containing the conductive material is continuouslydischarged, and the second composition containing the conductivematerial is intermittently discharged.
 7. The method for manufacturing asemiconductor device according to claim 5, wherein a thickness of thefirst conductive layer is larger than a thickness of the secondconductive layer.
 8. The method for manufacturing a semiconductor deviceaccording to claim 5, wherein a pixel electrode layer includes the firstconductive layer and the second conductive layer.
 9. A method formanufacturing a semiconductor device comprising the steps of: forming afirst conductive layer having a frame-shape over a substrate having aninsulating surface by discharging a first composition containing aconductive material; and forming a second conductive layer bydischarging a second composition containing a conductive material in aregion surrounded by the first conductive layer having the frame-shape,wherein wettability of the first composition containing the conductivematerial with respect to the substrate having the insulating surface islower than wettability of the second composition containing theconductive material with respect to the substrate having the insulatingsurface.
 10. The method for manufacturing a semiconductor deviceaccording to claim 9, wherein the first composition containing theconductive material is continuously discharged, and the secondcomposition containing the conductive material is intermittentlydischarged.
 11. The method for manufacturing a semiconductor deviceaccording to claim 9, wherein a thickness of the first conductive layeris larger than a thickness of the second conductive layer.
 12. Themethod for manufacturing a semiconductor device according to claim 9,wherein a pixel electrode layer includes the first conductive layer andthe second conductive layer.
 13. A method for manufacturing asemiconductor device comprising the steps of: forming a first conductivelayer; forming an insulating layer over the first conductive layer;forming an opening in the first conductive layer and the insulatinglayer by selectively irradiating the first conductive layer and theinsulating layer with a laser beam to remove part of an irradiatedregion of the first conductive layer and an irradiated region of theinsulating layer; forming a second conductive layer having a frame-shapeelectrically connected to the first conductive layer by discharging acomposition containing a conductive material in the opening; and forminga third conductive layer inside the second conductive layer having theframe-shape.
 14. The method for manufacturing a semiconductor deviceaccording to claim 13, wherein the first conductive layer includes atleast one of chromium, molybdenum, nickel, titanium, cobalt, copper, andaluminum.
 15. The method for manufacturing a semiconductor deviceaccording to claim 13, wherein the laser beam is transmitted through theinsulating layer.
 16. The method for manufacturing a semiconductordevice according to claim 13, wherein the insulating layer includes anorganic resin.
 17. A method for manufacturing a semiconductor devicecomprising the steps of: forming a first conductive layer; forming asecond conductive layer over the first conductive layer; forming aninsulating layer over the first conductive layer and the secondconductive layer; forming an opening in the second conductive layer andthe insulating layer by selectively irradiating the first conductivelayer, the second conductive layer, and the insulating layer with alaser beam to remove an irradiated region of the second conductive layerand an irradiated region of the insulating layer; forming a thirdconductive layer having a frame-shape electrically connected to thefirst conductive layer and the second conductive layer by discharging acomposition containing a conductive material in the opening; and forminga fourth conductive layer inside the third conductive layer having theframe-shape.
 18. The method for manufacturing a semiconductor deviceaccording to claim 17, wherein the second conductive layer includes atleast one of chromium, molybdenum, nickel, titanium, cobalt, copper, andaluminum.
 19. The method for manufacturing a semiconductor deviceaccording to claim 17, wherein the laser beam is transmitted through theinsulating layer.
 20. The method for manufacturing a semiconductordevice according to claim 17, wherein the insulating layer includes anorganic resin.